Abstract In this paper, Finite-time control design of the Stewart mechanism is performed using the Type-1 Fuzzy terminal and Type-1 Fuzzy fast terminal sliding mode controllers. Manipulator has six hydraulic jacks or linear actuators and top plate has six degrees of freedom. Fuzzy boundary layer and fuzzy sliding surface are defined for the controllers to decrease the chattering and oscillation of the actuators. The dynamic equations are derived using the Lagrange method by applying the uncertainties and the super-twisting observer is developed to estimate the velocity of the hydraulic jacks. For eliminating undesirable chattering phenomena using the fuzzy logic, a set of type-1 fuzzy rules is used in such a way that approximates the boundary layer of the sliding surface. Moreover for better performance tracking of the controllers, the parameters of the terminal and fast terminal sliding mode controllers are optimized using the genetic algorithm. Integral of absolute error was defined as objective function. Simulations present the good performance of the fuzzy controllers in tracking the desired path of the top plate, high robustness in the presence uncertainty and reduction of noisy sensors.