Partial factor productivity (PFP) of fertilizer is an important index reflecting overall effect of soil fertility level and fertilizer application rate. Hence, fertilizer application rate has some impact on partial factor productivity of the fertilizer. Based on the questionnaire distributed to 212 potato farmers in 13 counties and 11 prefectures of Yunnan during 2008~2009, relationship between fertilization rate and PFP of the fertilizer in potato production was explored and fertilization of the farmers was evaluated in rationality. Results indicate that on average, N 285 kg hm^-2, P₂O₅ 149.1 kg hm^-2, and K ₂ O 111.9 kg hm^-2 was applied in potato production and in practice fertilization rate varied in the range of N 30~1 005 kg hm^-2, P₂O₅10.5~735.0 kg hm^-2and K₂ O 7.5~466.5 kg hm^-2, and the PFP of the fertilizers in potato production was 82.3 kg kg^-1, and the PFP of N, P and K fertilizers was 158.7 kg kg^-1, 278.0 kg kg^-1 and 416.3 kg kg^-1, respectively. The application rate of N, P and K was in negative exponential relationship with their respective PFP, and so was the application rate of the fertilizers in all with the total PFP, with correlation coefficient being 0.873^﹡﹡, 0.872^﹡﹡, 0.801^﹡﹡ and 0.805^﹡﹡respectively. When the application rate of N 150~250 kg hm^-2, P₂O₅45~90 kg hm^-2, and K₂ O 90~120 kg hm^-2, was set as the rational range of fertilization rate, only 21.6%, 30.7% and 10.8% of the farmers in the survey were termed rational in N, P and K fertilizer application, respectively, in potato production in Yunnan province.