This paper mainly investigated the nonlinear dynamic behavior of diaphragm coupling systems with angular misalignment. First of all, a dynamic model is built according to the characteristic of diaphragm coupling with angular misalignment,whose dynamic differential equation is deduced by the second Lagrange equation. Later,the differential equation is solved by the numerical method. And bifurcation diagram of the systems with the speed changing and the angular misalignment changing are drawn,also the diagrams of displacement response,rotor orbit and phase trajectories under different speeds. And then appropriate nonlinear dynamics are analyzed for these diagrams.