Abstract—The present research uses a simple and direct method to assess the hazard rating of potential debris flows in Changhua County of Taiwan based on field investigation and numerical simulation. Taking 7 potential debris flow areas in Changhua County as the research objects, linear combination is utilized to evaluate the hazard rating of debris flow disaster in disaster-prone areas. In addition, Analytic Hierarchy Process (AHP) is applied to design the expert questionnaire for determining the factor weight, and pair-wise comparison is used to calculate the eigenvector as the weights of criteria. The calculated weights are further used for the hazard assessment. In addition, scenario simulations by FLO-2D can offer information which was not obtained in the current investigations. The priority of hazard rating in the 7 potential debris flow areas can be obtained based on this assessment.