Abstract: An experiment was conducted on a self-made test equipment to test the chopping properties of wheat straw under different conditions. On the basis of testing results, main cutting curves of wheat straw were given, under different cutting speeds of rotatory blade with different straw lengths, moisture centents cutting positions, different thicks knife edge, with and without shear bar. The curves showed that the moisture contents of straw and the shear bar are main impact factors to the cutting ratio besides cutting speed. The speed of 40m/s is necessary to cut off wet straw.