Abstract: In order to solve the problems that the seeding rate was large, the position of dropping seeds was inaccurate and the distribution of seeds was poorly uniform on seedling trays during northern japonica rice seedlings in greenhouses, a new directional precision seeding device with combined V-shaped groove slide was developed. It could achieve that each rice seed was seriately arrayed in its long axis direction by the positioning conveying plates, which moved along the D-shaped trajectory in the V-shaped slide. This device was mainly composed of test-bed bracket, driving system, combined V-shaped groove slide, cleaning-seed brush roll, seed separating and feeding mechanism, and horizontal conveyer system. The combined V-shaped groove slide and the seed separating and feeding mechanism were key parts of the seed-metering device. The chief function of the former was to arrange the seeds in their long axis direction while the seeds moved along the combined V-shaped groove, and the latter could drive the directed seeds to move towards the exit intermittently. The working process of the device would be as follows: the rice seeds were placed in the hopper above the combined V-shaped groove slide at first, then the positioning conveying plates drove the seeds to move towards the exit intermittently; each seed moving in the V-shaped grooves would constantly readjust its own long axis direction influenced by the action of the positioning conveying plates and the inclined plane of the grooves, which made the seed in the long axis arranged in a row along the V-shaped grooves slide, and realized the automatic orientation of the seeds. Later, the directed seeds were conveyed to the exit and located on the seed tape or seedling trays according to the required number and spacing of seed. To study the influence law of different factors on seeding performance for directional precision seeding device and obtain the optimal combination of parameters, the conveying frequency, the tooth spacing and the slide angle were taken as the main impact factors of the seeding device performance. In the self-made test-bed, the long-grain type japonica rice Dong Nong 419 was selected as experimental material, the effects of the 3 main impact factors on seeding qualified rate (1-3 seeds every turn), ideal seeding rate (2-3 seeds every turn) were studied by single factor experiments and three-factor and three-level orthogonal experimental design, and the relationships between 3 main influencing factors and seeding qualified rate and ideal seeding rate were established respectively by regression analysis. The influence law of the factors and their interaction on seeding qualified rate and ideal seeding rate was analyzed, and the best optimized combination of the parameters was obtained. The results indicated that the order of primary and secondary factors affecting seeding qualified rate was: conveying frequency > tooth spacing > slide angle and that affecting ideal seeding rate was: tooth spacing > conveying frequency > slide angle. The optimal combination parameters were conveying frequency of 2.7 Hz, slide angle of 46.8° and tooth spacing of 9.6 mm. Under the combination condition of the optimal parameters, the seeding qualified rate and the ideal seeding rate were 98.75% and 84.8% respectively. The seeding verification test indicated that the result fitted in well with the optimal experiments. The seeding overall performance test was carried out under the same conditions with 3 varieties of long-grain type japonica rice seeds (Dongnong 419, Longyang 16 and Daohuaxiang) and 2 varieties of short-grain type japonica rice seeds (Kongyu 131 and Longjing 26). As the paper tape moved at the speed of 0.04 m/s, the average qualified rate and the ideal seeding rate were 97.22% and 77.57%, respectively, and all the miss-seeding rates and reseeding rates were less than 2.6% and 0.4%, respectively. Experiment results indicated that when seeding long-grain type and short-grain type japonica rice seeds, the device had a better adaptability for the long-grain type. The seeding performance could meet the requirements of precision seeding for the japonica rice. The research provides a theoretical reference for optimizing the design and improving seeding performance of the directional precision seeding device for northern japonica rice.