Based on the CGDPA(China gauge-based precipitation daily analysis dataset)and PM-Ep(potential evapotranspiration calculated by Penman-Monteith)datasets during 1980-2016, the standardized precipitation evapotranspiration index(SPEI)and six evaluation indicators were used to evaluate the performance of CRU precipitation(CRU-P)and potential evapotranspiration(CRU-Ep)products for monitoring the temporality of drought events in mainland China. The results showed that the spatial distribution characteristics of CRU-P and CGDPA feature better similarity in mainland China, while CRU-Ep and PM-Ep are obviously different, but they are more accurate in most areas. SPEIc(SPEI value based on CRU-P and CRU-Ep)had a good performance in eastern and parts of western China. The correlation coefficient between SPEIc and SPEIm(SPEI based on CGPDA and PM-Ep)is greater than 0.7, the root mean square error is less than 0.8 and the hit rate is greater than 0.6 in eastern, northwest and southwest China. The SPEIc with different timescales, which was assessed by using the probability of drought event, mean start time error and mean end time error proposed in this paper, has a high accuracy in monitoring the temporality of drought events in most parts of mainland China, and it is better in eastern China than in western China. SPEI based on long series CRU products can be applied to drought monitoring in eastern, northwest and southwest China.