The Hsp70 gene plays an important role in the animal immune response.It can stimulate cells of the innate immune system directly.To understand the defense mechanisms of mud crab Scylla paramamosain, fluorescent real-time quantitative PCR was carried out to investigate the distribution profiles and expression patterns of Hsp70 before and after stimulation with the bacterium Vibrio alginolyticus and exposure to high salinity of 35‰.Hsp70 mRNA was highly expressed in hepatopancreas and all tissues examined, including muscle, stomach, heart, haemocytes, gill, epidermis, midgut, brain, thoracic ganglion, but it was less strongly expressed in the eyestalk.The expression of Hsp70 showed a clear time-dependent response after challenge by V.alginolyticus and exposure to high salinity of 35%o.The results indicate that Hsp70 may play important roles in mediating the immune response of bacterial challenge, and the activation of high salinity.