This paper proposes a parameter adaptive sliding mode control algorithm to address the generalized position tracking control issue for a Stewart Platform in the presence of parametric uncertainties and external disturbances. First, nonlinear dynamic equations of the Stewart Platform are extracted by the Lagrange method. To improve the performance of the conventional sliding mode control method, the parameter adaptive technique is applied to estimate the switching gain, which not only reduces the chattering phenomenon, but also avoids the conservatism of the controller. A rigorous stability analysis is given to prove that the tracking errors are uniformly ultimately bounded by Lyapunov stability theory. Numerical simulation results verify the effectiveness of the proposed control algorithm.