Abstract: Acrylamide is a kind of chemical material which was used for curtain-grouting in many hydroelectric projects. However the time-variant effect of the material has been studied rarely. Taken Chencun Water Power Station as an example, it is studied synthetically on the basis of the detailed monitoring data, investigation in situ, and analysis in Lab. It is pointed out that the effect of anti-seepage and uplift pressure reduced due to acrylamide curtain under dam sections 7 to 17 in generally good and steady state. However, its effect of anti-seepage seems to be weakened locally.The special attention should be paid to this abnormal phenomenon and if necessary, some observation and measures must be taken,so as to ascertain the normal operation of the project.