In order to analysis inner mechanical damage mechanism of soybean seed and the impact to its germination, three mechanical threshed soybean varieties mainly cultivated in Liaoning Province were selected. By means of stereomicroscope system and germination test, the inner mechanical damage impact to germination were tested, and the results showed that soybean seed germination ratio with inner mechanical damage was lower than 10%, main inner damage forms were devided into cotyledon break, cotyledon crack, radicle crack and hypocotyl break, which has remarkable latent harmfulness to soybean production. 