This study was conducted to investigate the effects of three different concentrations (6%, 8% and 10% final volume) of dimethyl sulfoxide (DMSO) on cryopreserved sperm of grass carp (Ctenopharyngodon idellus). Grass carp sperm was suspended in Kurokura extender #2 and equilibrated at $4^{circ}C$ for 10 min. French straws (0.25 ml) of sperm were frozen from $4^{circ}C;to;-4^{circ}C$ at a rate of $4^{circ}C;min^{-1}$ and then ken $-4^{circ}C;to;-80^{circ}C$ at a rate of $11^{circ}C;min^{-1}$. The straws were kept at $-80^{circ}C$ for 10 min and finally stored in liquid nitrogen $(-196^{circ}C)$. The cryopreserved sperm was thawed in a water bath at $40^{circ}C$ for 30 sec and fertilization, hatching rate and larval malformation were compared with fresh sperm (control). The fertilization rate of post-thawed sperm was comparable (from 88.21% to 94.30%) to that of fresh sperm. However, hatching rate of all frozen sperm were significantly lower (P<0.05) than that of control. Additionally, the larval abnormality rate of frozen sperm was significantly higher than that of fresh sperm. The results indicate that DMSO could affect the quality of cryopreserved sperm of grass carp, and a freezing program and a proper extender composition should be further studied.