Abstract: Abstract: There are many uncertain factors in the amount of artificial feeding, which cause the waste of bait easily, moreover, a huge labor cost. The author briefly introduces the research status of automatic feeding machine at home and abroad, and points out that the existing quantitative feeding machine cannot take both the structural simplicity and functional perfection into account. Aiming at the complex structure and expensive price of the volume quantitative baiting machine, the author studies and designs a simple baiting machine for marine crabs. In the modern factory circulating aquaculture system, each crab is placed in separate baskets. Its amount of feeding and feeding time are strict, which needs to be adjusted according to the weight and food intake of the crabs. As a result, the designed feeding machine must have a stepless adjustment according to the real-time status of the breeding objects with the ability that can vary the amount of bait, simple structure, stable performance and easy maintenance. Therefore, based on the principle of variable volume method, this paper designs an automatic feeding system for single-cage culture sea crabs with a strong anti-interference ability, which overcomes the shortcoming that the accuracy of quantitative weighing method is susceptible to vibration. The author introduces the basic structure and basic working principles of this system. The whole feeding system consists of hopper, rack, lower barrel, lower barrel, motors, Scissor mechanism and control system. When the MCU sends the start command, the upper and lower valves remain closed, and the material level photoelectric sensor detects whether the storage hopper has material. If there is material, the upper motor moves to open the valve plate between the storage hopper and the lower barrel, and the baits fall into the lower barrel. After the barrel is filled with bait, the upper valve plate is closed and the lower valve plate is opened for feeding, when the single chip transmits a signal for adjusting the amount of the feed, the middle motor operates to change the total volume of the lower cylinder by varying the height of the lower barrel, thereby realizing variable quantitative feeding. The programming controller (microcontroller) performs automatic control, and the touch screen realizes human-computer interaction operation. Then with combination of theoretical calculation, the paper determines the relationship between different quantitative volumes and motor control time. The second chapter optimizes the scissor lift mechanism to obtain the most efficient initial angle. The article also designs the control system, introduces the composition of the control system and the selection of the execution motor, details the operation of the control system during the work process, and briefly introduces the hardware of the human-computer interaction interface. Combined with automatic feeding system control circuit of the mater controller, it realizes the intelligent control of the entire automatic feeding system, leads to the system to be more convenient and intelligent. As for software, an interactive software is designed to implement functions such as parameter setting, working status, historical data query, and help interface, which helps new users quickly master the use of the feeding machine. Based on the automatic feeding systems for single basket of crabs breeding, the author experimented in Xinyi fresh aquatic Ltd. (Xiangshan, Ningbo) to test the function of casting bait at accurate time and quantity. After experiment, the performance test of the precision error of the feeding system shows that the design scheme is effective and feasible. On the premise of precise time point, the system can control the average error of feeding accuracy to less than 8%, which meets the needs of Marine crabs farming in factory. The test results show that the overall design scheme of the system is effective and feasible within the allowable error range of the factory aquaculture industry, especially in the case of a large feeding amount. To achieve automation and intelligent farming of factory-based aquatic products, reduce farming costs and improve the quality of marine crabs.