The goal of the paper is to propose an approach for analysis of load sharing in the planetary gear drives with a floating sun gear based on a stiffness model for multiple gearpair contact under consideration of the mesh stiffness of the engaged teeth, as well as the tooth gaps due to manufacturing errors and deviated position of the sun gear. The tooth stiffness of gears is expressed analytically considering the bending deflection and the contact deformation. The relations for tooth gaps due to various errors are derived from the mesh relations of gears based on the exact involute gear geometry. The balanced position of the floating sun gear is solved iteratively by using the load equilibrium conditions and the shared loads at the corresponding position of the sun gear. Finally some numerical examples are illustrated. The results calculated by the proposed approach have an acceptable agreement with those by using FEM.