In this paper, yield and reduction of the Dianchi Lake basin point source pollution load of the past 20 years were calculated and the change trend and reasons to it were analyzed. The results indicated that point source wastewater, COD, total nitrogen and total phosphorus discharge from the whole Dianchi Lake basin in 2007 were 26 368 t, 55 913 t, 11 222 t and 1 008 t respectively, and compared to that of 1988, the growth rate of those mentioned above were 73.69 %, 203.27 %, 246.99 % and 301.55 %, among which the growth rate of living pollution were 174.43 %, 296.58 %, 342.90 % and 462.86 % respectively, however the industry pollution has been controlled, the pollution load was decreased by 36.43 %, 6.36 %, 49.24 % and 69.87 %. With the cooperation of 8 sewage treatment plants and 2 pumping stations, from 1993 to 2007, the reduction of COD, total nitrogen and total phosphorus discharged from the Dianchi Lake basin increased from 1 542 t, 177 t and 13 t to 40 581 t, 5 193 t and 637 t, which was the main reason that the environment of the Dianchi Lake stopped worsening. It can be concluded that, living pollution is the main pollutant source, and the major factor to the growth of pollution load in the Dianchi Lake basin.