The permanent magnet slip clutchelectronically controlled hydraulic power steering system which is referred as P-ECHPS was proposed. The speed control model of permanent magnet slip clutch (PMSC) which is the key transmission part of P-ECHPS was established and all subsystems of P-ECHPS including of mechanical systems, hydraulic systems and three degrees of freedom steering dynamics system were also established in Matlab/Simulink. The variable assist characteristic curves were designed by analyzing the requirements of steering system under different speeds. According to the variable assist characteristic curves and the model of steering pump, the ideal speed of steering pump was obtained. For P-ECHPS containing various uncertain factors during steering process, such as parameter perturbation and external disturbance, and requirement of fast response, the adaptive nonsingular fast terminal sliding mode was used to control the speed of PMSC. Further it can realize the indirect control of P-ECHPS. The controller was designed according to the adaptive nonsingular fast terminal sliding mode control strategy. Through simulation, the results show that adaptive nonsingular fast terminal sliding mode control can ensure the output speed of PMSC track to the ideal speed quickly and has great robustness. The convergence rate of adaptive nonsingular fast terminal sliding mode control respectively increased by about 82.9% and 66.7% than that of sliding mode control and nonsingular terminal sliding mode control. It can also realize variable assist characteristic accurately to meet the handling stability and energy efficiency.