Abstract: In order to explore the time-domain mutation characteristics and evolutionary mechanisms of drought events in the Songhua River Basin, the standardized precipitation evapotranspiration index at the 12-month scale(SPEI-12) was calculated based on the precipitation and temperature data from meteorological stations in the Songhua River Basin during 1960～2020.The mutation of the SPEI-12 sequence was identified to explore the inter-annual mutation and underlying causes of drought events in the Songhua River Basin.By means of cross-wavelet transform, wavelet-coherence analysis, and lag-correlation analyses, this paper analyzed the spatiotemporal characteristics of SPEI-12 before and after the mutation and revealed the response of SPEI-12 index to the teleconnection factor.Results revealed that the mutation of SPEI-12 occurred around 1984,and SPEI-12 tended to decrease in the basin generally.The decreasing trend was more evident in the southeast of Hulun Buir City, the northwest of Qiqihar City, surrounding Heihe City, and the northern part of Jilin City than other regions.There was a resonance period between SPEI-12 and Pacific Decadal Oscillation(PDO) and El Ni1o-Southern Oscillation(ENSO),indicating that PDO and ENSO significantly interacted with SPEI-12 after the mutation.The lag-correlation characteristics between SPEI-12 and the two teleconnection indices significantly changed.After the mutation, the SPEI-12 and PDO showed a 1～12 months lag significant positively, and 6～8 months lag significant positively for ENSO.The analysis indicates that PDO and ENSO are critical to the mutation of drought characteristics in the Songhua River Basin.