In order to analyze the small signal stability issue, something which may occur as renewable energy sources connect to the grid, this paper applies power system small signal stability dynamic assessment and proposes the use of DSA Tools software to comprehensively evaluate the small signal stability. By adopting methods such as eigenvalue analysis, contingency analysis, single machine infinite bus scan and small signal stability limit search, it analyzes the small signal stability of the IEEE14 and IEEE145 bus test networks. The results show that the IEEE14 bus test network has better small signal stability, but that of the IEEE145 bus test network is worse. Moreover, it is indicated that DSA Tools software and SSAT analysis tools could be applied to the design of an early warning scheme for power system and the optimization of a system protection framework strategy. This work is supported by National Natural Science Foundation of China (No. 61440030) and Research Program of Henan Natural Science Foundation (No. 162300410259).