On the basis of the catastrophe theory，the maximum likelihood estimation method and the correlation coefficient method，an improved method for risk analysis of rock slope is proposed. And the rationality is verified by an example. The right abutment slope stability of Qianping Reservoir is taken as the research object. The slope risk evaluation system is constructed. And the conventional evaluation value is calculated based on the catastrophe theory, and the corresponding hyperbolic function is obtained by data fitting. The initial conversion value of the evaluation index is substituted into the obtained hyperbolic function to obtain the improved slope risk evaluation value. The improved mutation evaluation value is compared with the conventional mutation evaluation value. Results show that the result of the evaluation by the catastrophe theory which are too concentrated and big are improved by the approach, which makes it is more conducive to the determination of the degree of slope risk.