Abstract: The diurnal variation rule of water qualities was illustrated in enclosures which is in heavy polluted Fubaowan Bay, Lake Dianchi.There are 2 enclosures of without agent addition. While another 4 enclosures with inactivated agent addition, and the agent consisted of aluminium salts, calcium salts and claies. It was 67%~90% diurnal variation rate of total phosphorus (TP) of water in added inactivated agent enclosures apparently higher than the rate of un-drugged enclosures which was 48%~53%. The day decreased rate of total nitrogen (TN)of water in added agent enclosures was 15%~28%, but the decreased rate of un-drugged enclosures was -7%~-18%.The average-day change rate of turbidness and chlorophyll a of agents addition enclosures was 62% and 51% respectively, which apparently higher than that of enclosures without agents addition, in these enclosures, the turbidness average-day change rate was 43% and chlorophyll a average-day change rate was only 35%. Comprehensive analysis was made on the influence of inactivated agent addition on water quality and nitrogen transferring and translating. The results shown that in the enclosures with inactivated agent addition, the pH value and DO concentration was increased, the diaphaneity of overlying water was improved, the biomass of alga and concentration of organinc nitrogen in the overlying water were decreased. The water qualities gained improving obviously.