Wind energy is believed as one of the most efficient clean renewable energies and is explored more often currently. The dynamic behaviors of wind turbine gearboxes are concerned by engineers since they affect the whole working performances and the service lives of wind turbines. In this work, a coupled dynamic model is developed for a wind turbine gearbox with flexible pins. For the planetary gear stage, the sun gear is floated and the planetary gears are flexibly supported by flexible pins. The sub-transmission system of the gearbox, which consists of a planetary gear stage and a parallel gear stage, and the body sub-system are coupled through the bearings which are simulated as springs. The dynamic behaviors of the system are studied using a lumped parameter model, in which the stiffnesses of the gearbox body is predicted using the finite element method, the results is also verified by experiments conducted on a test rig. (C) 2014 Elsevier Ltd. All rights reserved.