A vehicle-bridge coupling vibration model of a moving spring mass system has been constructed based on mode superposition. Based on Duhamel term′s precise integration method (PIM), Cotes and Gauss algorithms are introduced to solve the nonhomogeneous linear differential equation following the load in an integration step be regarded as coordinating load and constant load. Taking a spring mass system running on simple supported beam as an example, the effects of equivalent nodal load and numerical algorithms for nonlinear differential equation based on Duhamel term are analyzed. The results indicated that the result of Cotes with coordinate load is closer to analytical solution. The way of equivalent load has weak effect on Newmark-β numerical result in vehicle-bridge coupled vibration response. But the results also show that the response curve of vehicle bridge coupling vibration disperse when the equation is solved using Gauss numerical method with coordinate load, and undermined coefficient method has overlarge error at the same time. Research results show that Newmark-β method can meet the engineering accuracy. In order to get the same accuracy as PIM-C-H, Newmark-β method need smaller time integral step and cost more time accordingly in solving the same problem.