An approach of loaded tooth contact analysis is proposed for analyzing the load sharing and the load distribution of cycloid planetary gear drives with multiple tooth pairs contact. The mathematic equations of cycloid gear profile are derived from kinematic relation of the gear and the pin wheel. The analysis of tooth contact is based on instant center method. The contact stresses of the multiple engaged tooth pairs are calculated based on the influence coefficient method. An analytical, simple relation for calculation of the load sharing and the max. Hertzian contact stress with the assumption of constant meshing stiffness is also proposed for comparison. Finally, a study case was analyzed for load sharing and contact stress distribution of engaged tooth pairs by both methods. The characteristics of the contact stress of the cycloid planetary gear drives are clearly identified.