The effect of different mowing heights which were 10cm, 20cm and 40cm on red clover growth characters, net photosynthetic rate and maximal photochemical efficiency of PSII（Fv/Fm） were investigated. The results showed that at the 20cm stubble height, red clover had the higher photosynthetic efficiency, longer effective photosynthetic time, moderate tillers, more branches and high total product, which was conducive to the sustainable production of red clover. Therefore, the suitable mowing height of red clover was 20cm.