Abstract: Slope disaster, as the most frequent type of sudden geological disaster with the largest number in Beijing, is the focus and difficulty of geological disaster prevention and control in Beijing. Its inducing triggering factor is mainly rainfall. How long rainfall has an impact on slope deformation in Beijing is still mainly based on qualitative and empirical judgment. Therefore, this paper selects the 2021 flood season slope disaster in Huairou District of Beijing and Shijiaying huiqingjian landslide in Fangshan District as the research samples, and analyzes the correlation between slope disasters and 24 h rainfall from 1 to 30 days before the disaster. The statistical analysis shows that the slope disaster in Beijing has the greatest correlation with the rainfall in the previous week. The research conclusion can be used as an important reference for slope disaster early warning in Beijing.