The classical PID controller is based on the concrete model of the object and is only suitable for the design of linear control system. Step servo system is a typical nonlinear system, so the intelligent control strategies should be adopted. In this paper an approximate model of the step motor is presented, a compound fuzzy PI controller is designed to fulfill the control of the step motor, and is successfully applied to the automatic control the scanning device of eddy current nondestructive testing (ECNDT). The proposed controller is robust to load torques, cogging forces, and other disturbances. The fuzzy PI controller also guarantees asymptotic stabilization and possesses better dynamic performance compared with the traditional PID control algorithm. The simulation study and an experimental validation carried out on the automatic control system of the scanning device confirmed the suitability of the proposed approach.