Based on synchronous observation data of small evaporation pan and E-601 evaporation pan in 16 stations, taking Nanjing station as an example, the ratio method and multiple linear regression method were used to estimate and verify small pan evaporation in the long-term time series. Results showed that:month conversion coefficient estimated by ratio method varied between 0.490 and 0.609, while the year conversion coefficient varied between 0.476 and 0.621, whereas the average conversion coefficient of the two were the same, i.e. 0.537, the monthly data correlation coefficient of two kinds of pan evaporation was 0.952 4, while annual data correlation coefficient was only 0.496 2, which indicated that the monthly conversion coefficient was more reasonable and applicable when ratio method was adopted; the multiple linear regressing equation of small pan evaporation based on meteorological factors and monthly E-601 pan evaporation was ideal, while the determination coefficient was between 0.809 and 0.940; in the simulation test of ratio method and multiple linear regression method, annual average error of ratio method was 7.9%, and that of multiple linear regression method was only 2.5%, the forecasted result determinate coefficient of ratio method was 0.861 9, and that of the multiple linear regression method was 0.953 4 which was much better. In conclusion, small and E-601 pan evaporation conversion coefficient of each station in Jiangsu province was offered from this paper, providing reasonable basis for effectively by using long-term small pan evaporation in Jiangsu province.