Abstract: There are many contradictory reports about the sperm spike of shrimps.The structure, biochemical composition and function of sperm spike in freshwaterprawn Macrobrachium rosenbergii were studied in this paper by using cytochemical techniques and electron microscopy.The sperm spike of the shrimp has a crossstriated appearance.The flocculent materials in the middle of the cross section nearthe tip of the spike may represent the phosphatase.The spike is composed primarilyof protein as indicated by positive mercury bromphenol blue staining.The negative feulgen reaction means no DNA present here, which is significantly different fromthat of reptantian.Part of the spike contains acid phosphatase.Unlike the flagellate inthe typical sperm, this spike is non-motile,The incorporation of the sperm into egg isthrough the spike penetrating into firstly and the base following in finally, whichsuggests that the spike could play a role of acrosome.