In this study, numerical simulation of damage identification of simple supported beam bridge model is performed by using modal curvature norm as damage characteristic parameter. Considering the influence of temperature on damage identification, the principal component analysis method is used to remove the damage, and then the minor damage identification of the simple supported beam bridge model is realized. The mechanism of temperature effect, numerical simulation and elimination method of temperature influence are introduced at first; then in consideration of the various slight damage and different temperature conditions in the simple supported beam model，the results of damage identification using the modal curvature norms before and after eliminating the temperature effect were discussed. In the end, the conclusions are drawn as follows: temperature variation may adversely affect the damage identification of the members, even cause false recognition; modal curvature which is eliminated the influence of temperature by PCA, can provide accurate localization of the slight damage and the damage extent quantification.