Abstract: The level,regularity,effective phase and continuance of immuneresponse of grass carp immunized with vaccine CFRV were approached in thispaper. Strong response,both more than 80% of percent relative protection (PRP)and significantly higher antiserum neutralization titre(ANT) than control, couldbe produced after immunization. The effective phase of immune response was wi-thin five days and the high level of ANT was reached on the tenthday.On the twenti-eth day, ANT went up to peak level and remained for twenty days then it fluctuated at this level. This research proved that the continuance of immune responseof grass carp immunized with vaccine CFRV was beyond thirteen months.