In this paper the two-point estimate（TPE） based method is proposed for probabilistic small signal stability（PSSS） analysis of power systems considering the uncertainties in system parameters， load and operating conditions， et al. In this method， the TPE method is outlined together with the calculation procedure， and the stability indices and the judgment of unstable types for power system PSSS are calculated. Compared with the widely-used Monte Carlo simulation method， the TPE based approach can estimate the statistical characteristics of random variables with less calculation cost while keeping enough precision. Simulation results of a 2-area power system show the effectiveness of the proposed algorithm. The proposed methodology can be extended to other applications in power system with uncertainties.