The traditional framework structure of airborne photoelectric platforms limits their load ratio. A new series spherical mechanism could solve this problem, but there is no kinematic model to support the design. Based on the D-H parameter method, the forward and inverse kinematics models of the series spherical mechanism were established. The kinematic model was solved using MATLAB, and the correctness of the model was verified by comparison with ADAMS, a multi-body dynamic analysis software.The experimental device was set up to collect and perform the kinematic model verification experiment.The results show that the experimental error between the calculated value and the measured value of the kinematics model in the experimental equipment is within 5% and is mostly a result of machining adjustment error and sensor measurement error in the experimental system. The model established provides a solid foundation for application in research on optoelectronic platform visual axis pointing control based on a spherical mechanism.