Steam Generator is a highly complex nonlinear time-varying system. In this paper, linear parameter varying theory was proposed to build the polytopic linear parameter varying model of steam generator. According to the method of linear-quadratic regulator which contains the H∞ performance, a gain-scheduling tracking controller was designed based on polytopic linear parameter varying model. Linear matrix inequalities technology was used to solve the controller. The simulation results show that the controller has good tracking ability, and can restrain the disturbance effectively.