Abstract: In order to investigate the dynamic behavior of heat transfer tube under the influence of both internal and external flows, an analytical model of the coupling system was developed. The wake oscillator model was introduced to present the analytical model. Meanwhile, the mean axial extension of the tube was also considered. The nonlinear coupled equations of motion were discretized by employing the Galerkin method. Based on numerical simulations, the effects of internal and external fluid flow velocities and nonlinear parameters on response were studied. Moreover, the bifurcation diagram and phase portrait for vibration amplitude with various external fluid velocities were constructed. The results show that the tube displays various dynamical behaviors around the post-buckling configuration such as inverse period-doubling bifurcation, periodic and chaotic motions.