Based on the dynamic nodal loading approach, the traffic load excitati on was transformed into the equivalent nodal excitation. Then, the two step iden tification method was used to identify structural parameters of a bridge. Firstl y, the New markβ method was employed to transform the equation of structure motion, and a new form of motion equation came into being, and the measured acceleration was used to construct the displacement, velocity and acceleration responses in the t ransformed space. Secondly, the structural parameters were identified using the recurrence formula constructed by the leastsquare method. The method proposed i n this paper offers an efficient approach for bridge structural parameter identi fication under traffic excitation. The numerical simulation results show that th e method can identify the structural parameters of a bridge excited by traffic loads accurately and rapidly.