Abstract: Acoording to the problem of loss sowing detection of pneumatic rapeseed precision seeder, one detection method based on seeding frequency was put forward. Using frequency measuring equipment the seeding frequency at the outlet of pneumatic metering device was tested at different rotational speeds and different seeder hold blockages and through the frequency three areas, named loss less sowing area, loss sowing area and serious loss sowing area, have been defined to estimate the degree of loss sowing. The method of loss sowing detection in field has been designed. First through smoothness processing for the real-time measuring rotational speed of metering device and interpolation operation of the frequency threshold value which was used to estimate the deep of loss sowing could be obtained. Through comparison with the median filtering measuring frequency and the frequency threshold value, the depth of loss sowing can be estimated. The tests on test-bed indicate that the method based on seeding frequency can effectively detect the degree of loss sowing, and when there is no loss seeding, the accuracy rate can be achieved to 100 percent. While up 8 seeding holes are clogged, the condition of loss seeding could also be detected with the accuracy of 100 percent. The method also can avoid continually alarming problem aroused by occasional loss seeding.