Abstract: Power spectrum density function is one of the main parameters used to describe random vibration. It tells the main affecting frequency. A study on the power spectrum density would reveal the physical principle of vibration and some methods to control random vibration could be found. This study was aimed to control small amplitude output power spectrum density of soil-engaging machine components of precision seeder in order to obtain an ideal field seed distribution to meet with agricultural requirements. Results showed that the peak value of self-power spectrum was mainly affected by the transmission function H_1a(ω) ,the self-power spectrum density function G(ω/Ω) ,and cosw . Based on the study, rubber depth band, rubber presswheel, bumpers made of air spring and profiling compensation devices were developed. By using those components together with a certain working speed,the peak value point could be avoided. The indoor soil bin test showed that the theoretical study was in consistent with the experiment. It also proved that bumper and profiling compensation device were important for decreasing vibration and stabilizing seeding depth. A field production trial was also conducted under the condition of prepared seed-bed. Results showed that the coefficient of variation of seeding depth was only 13. 4% with the average seeding depth of 4. 88 cm under 9. 05 km/h seeding speed. The field seedling counting showed that the components were beneficial to maintain evenness of seeding depth and also good for water conservation,especially under dry conditions.