The evolution pattern and development trend of secondary debris flow in the strong earthquake area were significantly affected by the “post-effect” of the earthquake. The peak discharge had increased several times compared with that before earthquake, and the scale of the debris flow had increased obviously. According to the norms, the new challenge to the targeted design of prevention and control of the gully debris flow in seismic area is being put forward. Therefore, based on the case of debris flow in Wenchuan earthquake, the factorial regression analysis was used to investigate the intrinsic relationship between the basic characteristic parameters and the peak discharge in this paper, and a multivariate prediction model was established. The problem of information superposition caused by the collinearity of the original variables was solved, with goodness of fitting R2=0.94, and the prediction accuracy was improved significantly; at last, the proposed model was used to predict the peak discharge thresholds of 32 debris flows in the study area, and the distribution law of dynamic characteristics and the scale evolution characteristics of debris flow were analyzed in strong earthquake area. Based on results above, the characteristic parameters of “super-large-scale high-level long-distance debris flow” was defined.