Abstract: The pumping well diagnosis is an important research subject of sucker rod pumping system in oil field. In this paper, the three-dimensional dynamics equations of sucker-rod based on the actual well path was numerically analyzed by finite difference method on time and space discrete, and the relationship between load and displacement of sucker rod string motion of arbitrary cross section in one cycle, was iterative calculated with actual measured near-surface dynamometer cards as the boundary condition. The calculated results could provide a quick and accurate diagnosis of sucker rod pumping system, and the correctness of diagnosis results was validated by actually data for the fist time. The diagnosis results of pump dynamometers show that the diagnosis method presented in this paper has good accuracy and the error between simulation and actual measured down-hole dynamometer cards was less than 5%.