The change in the constitution of Macrobrachium rosenbergii hemocytes was observerd and the functions of different type hemocytes were speculated after PSB into the muscle of Macrobrachium rosenbergii as a exciter.Stained by Wright's staining,the staining slides were observed under the light microscope at 12,24,36,48,60 hours after received injections.It shows that hyaline cells normally constituted 66.62% of the total amount of hemocytes.In 24 hours after received injection,the ratio of hyaline cells to the total amount of hemocytes became to about 60%,after 36 hours,it declined sharply to nearly 30%,after 48 hours,it began to rise,and after 60 hours it recovered to 55%.The process of change is that the ratio declined slowly at first,then to declined sharply,and to recovered later.