The objectivity and accuracy of the analysis results of pollutant load into the Lake Taihu are controlled by the calculation precision. The paper takes Lake Taihu as an example, analyses not only pollutant load of rivers into Lake Taihu in 2010, but also the temporal and spatial distributions and variation of the pollutant load. The daily monitoring data of water yield and water quality under the existing monitoring network are used to calculate pollutant load into the Lake Taihu in a daily accumulation period, which is assumed the highest calculation precision for existing analysis and calculation of pollutant load of rivers into the Lake Taihu. With different monitoring schemes and different calculation methods, the study analysed pollutant load of rivers into the Lake Taihu and the calculation precision achieved. It is found that pollutant load of rivers into the lake analysed and calculated nowadays accounts for 80 percents of which monitored everyday simultaneously. Technical support is provided by analysing the calculation precision of pollutant load of rivers into the Lake Taihu to make scientific monitoring schemes and to improve the computation precision of the pollutant load of rivers into the Lake Taihu.