A dynamic fuzzy analysis method for the seismic reliability of collapse accumulation slopes was established, considering the randomness and fuzziness of parameters for rock and soil in collapse accumulation slopes and the excitation of bidirectional earthquakes. Furthermore, the influence of vertical earthquake excitation on the reliability of the collapse accumulation slope was analyzed. First, the dynamic time-history analysis of FEM was used to calculate the dynamic response of collapse accumulation slope under bidirectional earthquakes, and the strength parameters of rock and soil mass were processed using fuzzy theory. Based on the Mohr-Coulomb strength criterion, the time-history calculation model for the safety factor and reliability of the slope under an earthquake was then established. Finally, a new method for evaluating the seismic reliability of slope was adopted, and the corresponding program was compiled by MATLAB to realize the rapid output of calculation and analysis results. The calculation results of the proposed method are reasonable and safe for engineering. The vertical earthquake has an impact on the reliability of the collapse accumulation slope, but the degree of impact must be analyzed in accordance with the actual situation. For the working condition of the example, the vertical earthquake slightly influences the reliability of the collapse accumulation slope, which only reduces the reliability by 3.55%. Therefore, the influence of a vertical earthquake can be overlooked in this example, and only the influence of a horizontal earthquake should be considered.