Abstract： Aimed at the poor risk assessment effect resulted from index information asymmetry and the fact that the existing similarity measurement method can only deal with linear information, this paper proposed a risk assessment method based on flexible similarity measurement and possibility skewness. First, a method for flexible similarity measurement was proposed based on expanded generalized fuzzy number as adaptive fuzzy number, and its basic properties were proved. Second, the asymmetry of the index information was analyzed, and a matrix of possibility skewness was built. Finally, a risk assessment model was established by using flexible similarity measurement and possibility skewness, and the validity of the method was proved by taking practical example of tailing dam.