The distribution of early day sub-surface sea temperature of 0 to 400 meters(especialy 120 to 300 meters) in abnormal onset years of SCSSM is discussed in terms of composite analysis and correlation method.Results show that the anterior sea temperature in the North Pacific basin(150°E～150°W,35～50°N) has a profound influence on the onset dates of SCSSM.When the sea temperature of previous winter in the basin is lower,the onset date of SCSSM is later,and vice versa.A thermal parameter(I_tp) is defined to represent the underlying surface effect over the basin,and it is inferred that the influence of sea temperature anomalies on the onset date of SCSSM can be realized through atmospheric teleconnection.