In order to study the effect of moisture content on seed corn threshing mechanism, the typical three varieties of corn seed, such as Tiedan Ⅰ Generation 1 etc., were selected and a series of experiments for different moisture contents of seed damage strength, handle strength and threshingforce were completed. The test results showed that the effect of moisture content on corn threshing was mainly reflected in two aspects of seed damage strength and the threshing-force. There was a significantly increasing on damage strength of corn seed kernels as the moisture content down, and then the corn seed kernels were not easily broken during threshing. These main reasons were the lager longitudinal and lateral clearance, not extrusion or support among kernels, for the significantly dropping of the threshingforce with the moisture content decline, and the handle strength dropped at the same time too. The test results also showed that there was no longitudinal and lateral clearance among kernels when the moisture content was higher than 25%, the longitudinal and lateral clearance among kernels near the biggest changed slowly when the moisture content was below 14.26%.