In order to screen some potato varieties (lines) with high resistance to scab, the scab resistance of 36 potato variety (line) resources planted in Nanning city and Yulin city were comprehensively evaluated through the point of the incidence and disease index. The membership function method were used to analyze these field identification results in this study. The results showed that the incidence (x) and disease index (y) presented the normal distribution. y is the exponential function of x. Two potato varieties with high resistance to scab and one potato material with high susceptibility to scab were obtained. The results of field planting method are basically the same as that of artificial inoculation identification. These findings could provide reference for the prediction of potato scab disease and scab resistance breeding.