Summary: The expression of CH50 polypoptide in bladder cancer cell line BIU-87 and the effects on the invasion ability of BIU-87 were investigated. The eukaryotic expressing vector pCH510 of polypeptide CH50 was introduced into BIU-87 cells by gene transfection in vitro. The expression of CH50 polypeptide was detected by using immunohistochemical S-P method. The expression of the transfected gene was identified by RT-PCR. Cell invasion assay kit was applied to detect the effect of CH50 polypeptide on the invasion ability of BIU-87. The results showed that the BIU-87 cells transfected with pCH510 could express the CH50 polypeptide, while in the control group, no CH50 polypeptide was detectable. In the transfection group, the invasion ability of BIU-87 in vitro was lower than in control group (P<0.05). It was concluded that CH50 polypeptide was successfully expressed in BIU-87 cells by gene transfection, by which the in vitro invasion ability of BIU-87 was inhibited.