In order to explore the mechanism of koi’s anti-stress,the study was performed to examine the effect of continuous heat stress on non-specific immune parameters and HSP70 gene expression in Taisho Sanke koi under the laboratory conditions.Samples for detections of respiratory burst,complement protein 3(C3),superoxide dismutase(SOD),malondialdehyde(MDA)and relative expression content of heat shock protein 70(HSP70)were taken before stress,2,6,10,14,18,22 and 26 h after stress,respectively.The results were as follows.Respiratory burst activity decreased after stress,and it decreased significantly after stress 2,10,18-26 h(P<0.05).The content of serum C3 was increased slightly 2 h after stress.Compared to before stress,the level of serum C3 decreased 6-26 h after stress,and it decreased significantly 14-22 h after stress(P<0.05).The level of serum SOD had the trend of augment,but not significantly(P>0.05).The concentration of serum MDA increased after stress,and it increased significantly after stress 10-18 h(P<0.05).Compared to before stress,the relative expression content of HSP70 gene significantly increased by 5.93 times 2 h after stress and 2 times 26 h after stress(P<0.05).6-22 h after stress,the relative expression content of HSP70 gene had no significant difference from that before stress(P>0.05).These results indicated that heat stress affected non-specific immune parameters,and lowered non-specific immunity of Taisho Sanke koi.The expression of HSP70 gene was regulated by heat stress.HSP70 induced by heat stress played a role of stress protection to koi.