To illustrate the application prospect of nonviable probiotics in marine fish aquaculture,the present study evaluated the effect of dietary administration of viable and heat-inactivated autochthonous probiotic Psychrobacter sp.SE6 on the growth performance and serum immune parameters of grouper(Epinephelus coioides).225 juvenile fish with an initial weight of(14.6±0.2) g were randomly divided into 3 groups(groups T0,T1 and T2)with 3 replicates per group and 25 fish per replicate.The fish were fed for 60 d with basal diet containing 0 cfu/g(control group T0),1×10⁸ cfu/g viable Psychrobacter sp.SE6(group T1)and 1×10⁸ cfu/g heat-inactivated Psychrobacter sp.SE6(group T2),respectively.The results showed that,in the early period(0-30 d),the weight gain rate(WGR)and specific growth ratio(SGR)of the two probiotic groups were significantly higher than the control group(P＜0.05),and the feed conversion ratios(FCR)of two probiotic groups were lower than those of the control group.During the whole experimental period(0-60 d),the WGR and SGR of the two experimental groups were significantly higher than those of the control group(P＜0.05),the FCR of the two experimental groups was lower than that of the control group,and the FCR of group T1 was significantly lower than that of the control(P＜0.05).At day 30,the serum immunoglobulin M(IgM)and complement C3 contents in the experimental groups were higher than the control group,but not significantly(P>0.05).At day 60,the serum T-SOD activity,complement C3 and IgM contents in the group T1 were significantly higher than those of the control(P＜0.05),while the activities of T-SOD and lysozyme,complement C3 and IgM contents in the group T2 were higher than those of the control,but not significantly(P>0.05).In conclusion,both the viable and heat-inactivated Psychrobacter sp.SE6 played positive roles in promoting the growth performance and feed utilization,improving specific and nonspecific immune functions in E.coioides.Although better effect was observed in the viable probiotic group,the heat-inactivited probiotics have several advantages,such as high safety,stable quality and convenient processing and storage.Therefore,further study is needed to evaluate the application of heat-inactivated probiotcs in marine fish aquaculture.