Abstract: There were 20 cracks at upstream face dam head of Huanren dam during construction which threatened dam safety. So that upstream anti- seepage layer and mortar bar at the back were made before impounding. In 1981, 8 newcracks were found and 11 old cracks had expanded. According to this, measures were taken that highered the anti- seepage layer with asphalt concrete, made dam crest anti- seepage layer with asphalt felt and recast the capping plate with expansion perlite. After these measures, site inspection and monitoring showed that the dam seepage decreased, dam temperature rose, temperature difference minimized and the cracks turned stable.