A reliability analysis method for the seismic stability of collapse accumulation body, which both considers the bi-directional earthquake excitation and the uncertainty of rock and soil parameters, was proposed in this paper. The influence of horizontal and vertical seismic loads on the stability and reliability of collapse accumulation body was further analyzed. First, the safety and stability state of the collapse accumulation body under bidirectional earthquake was analyzed by using the pseudo static method and the limit equilibrium method, and the seismic limit state equation of collapse accumulation body was established based on the response surface method and the JC method. Then, the parameters of rock and soil were processed using the blind number theory, and the blind number model for the seismic safety factor of collapse accumulation body was further established. Finally, the corresponding program was compiled by MATLAB to realize the fast output of calculation and analysis results. The calculated results showed that: the calculation value of the proposed method is low, so it is more safe and reliable for projects. Compared with the horizontal seismic load, the vertical seismic load has little impact on the stability and reliability of collapse accumulation body, which only reduces the safety factor and reliability by 1.78% and 2.78%, respectively. Therefore, in this case, only the influence of horizontal seismic load needs to be considered when the quasi-static method is used for seismic analysis.