The tracking control problem for Flexible Joint Manipulator Control System (FJMCS)with unmeasurable states is addressed in this paper.Firstly,a High-Gain Observer (HGO) is con-structed to estimate the unmeasurable states and the uncertainties.Then,a Dynamic Surface Con-trol (DSC) scheme is developed by using the estimation of HGO.The newly proposed controller has two advantages over the existing methods:(A) a novel Spike Suppression Function (SSF) is devel-oped to avoid the estimation spike problem in the existing HGO-based controllers.(B) Unlike the existing observer-based partial feedback control scheme that can only estimate the unmeasurable states,the proposed HGO can estimate both the unmeasurable states and uncertainties.The closed-loop system stability is proved by the Lyapunov theory.Simulation results demonstrate the effectiveness of the proposed controller.