Abstract: Structural distortion of bridge contains rich connotation information of bridge structures and possesses the features of nonlinear, sequential and small sample capacity.In this article, the calculated model of bridge structural distortion is given out by application of support vector machine and the practical monitoring data of Hangzhou Bay Bridge are taken as the study object.The feasibility and effectiveness of evaluation over bridge structural health state have been proved through test, and the superiority of least square support vector machine in distortion calculation has been shown on comparison of test results.