This paper proposed a Gain-Scheduling Adaptive of a Proportional-Integral (GSAPI) controller scheme for speed control of three-phase induction motor (IM) drives using a particle swarm optimization (PSO) algorithm to optimize the parameters of the proportional-integral (PI) of the speed controller. The PI gains are allowed to vary within a predetermined range and therefore, eliminate the problems faced by the conventional fixed PI and PSO-PI without gain-scheduling control speed controllers. The performance of the proposed GSAPI speed controller is simulated and compared with the conventional fixed PI and PSO-PI speed controllers under different operating conditions. The tuning of PI speed controller parameters is determined by conventional fixed gains, PSO-PI without gain-scheduling control and on-line. For conventional PI, the PI gains are optimized by Trial-and-error method. For PSO-PI tuning, the PI gains are optimized by PSO. On-line application, PSO gains scheduling adaptively adjusts the controller gains to improve the speed response under different operating conditions. The simulation and experimental results show that the GSAPI can be efficiently used for tuning parameters of the PI speed controller, also a good improvement in transient as well as a steady-state response of the proposed controller over the conventional fixed PI and PSO-PI one.