Risk assessment on geological hazards and zoning is the foundation of geological hazards prevention. To solve the problem of uncertainty and incompatibility between quantitative and qualitative indicators, and the deficiencies of the indexes weight method, this paper establishes the model for risk assessment on geological hazards binding the extension theory with the optimal combination weighting method. With the matter-element model of the extension theory, the weight coefficients are calculated by using the optimal combination weighting method that can effectively use the experience of expert judgement and accurately reflect the utility value of the data, and can properly resolve the problem of weight allocation. Then, through calculating the correlation function value and relational degree, determine the actual geological hazard grades of study area. Finally, this paper applies this model in Hanyin County of Shannxi Province and gets the predicting results compared with AHP method and entropy method, and the results conform to the fact. It is proved that extension theory based on optimal combination weighting method is quite effective and available in risk assessment on geological hazards.
