The maximum likelihood method is used and the epidemic-type aftershock sequence (ETAS) model is fitted in the analysis of aftershock sequence characteristics of the April 14,2010 Yushu (M_S7.1) earthquake that occurred in Qinghai province.To examine parameter stability,ETAS parameters and their standard errors are estimated with different cutoff magnitudes,M_C,and different ending times for the fitting interval.The overall parameters are observed to be α=0.948 2,p=1.059 6,and b=0.817 3 with setting M_C=M_L1.5. Compared to other M>7.0 earthquake sequences on the continental China,the Yushu M_S7.1 earthquake sequence is characterized by a weak triggering capability in generating secondary aftershocks,and a quick decay rate of aftershocks.A systematic approach for using multiple cutoff magnitudes above the magnitude of completeness is adopted in the calculation process to examine stability of the sequence parameters and to analyze the degree to which they are affected.The cutoff magnitude,M_C,is observed to have a certain effect on the value of α,k,and p (with an increase in M_C the value of k decreases,there is a general increasing trend of α,but less influence on p).ETAS model parameters with different sequence durations are studied in this paper,together with their temporal variations and stability in the early stage after the shock.There is variation in the range of p and α shortly after the earthquake stops for different cutoff magnitudes within the same earthquake,whereas there is a trend of p and α is towards convergence and stability after stabilization of seismic activity.Furthermore,there is evident change in the temporal variation of ETAS parameters 14 days after the mainshock,when the parameters become relatively stable.