In this study, the CASA (Computer Assisted Semen Analysis) was employed to determine how sperm quality changes during the spawning season. The sperm quality parameters, including motility ratio, concentration, volume, VSL (Straightline velocity) and VCL (Curvilinear velocity), were examined at four phases during 7-weeks from the beginning of sperm production to the end, with 2-week as an interval time. The results indicated that all the indexes have different varying patterns during the spawning season. The motility ratio changed from 83.4% to 36.9%, the sperm volume varied from 2.50ml to 2.23ml, the concentration decreased from 1.08×108 ind/ml to 0.46×108 ind/ml and the value of VSL/VCL was reduced from 0.69 to 0.35. The findings on different changing patterns and the amount of variations could contribute to turbot aquaculture directly either in broodstock breeding and its sperm application.