In this paper,the problem of state observation for a class of nonlinear differential-algebraic equation (DAE) subsystem is considered and a design scheme of initialized high gain observer is proposed.There are two steps for this observer design.Firstly,the equivalent transformation of the system is achieved by a nonlinear diffeomorphism transformation.Then for the equivalent system,an initialized state observer design is given to make observation error converge exponentially.Finally,a numerical simulation is presented and the simulation results verify the effectiveness of the proposed method.