Abstract: It is a difficult task to control the temperature of semi batch polymerization processes, due to its strong nonlinearity, long delay, time varying, and complex mechanism. Moreover, the traditional cascade control structure cannot ensure that the temperature is controlled within the allowed error range. In this paper, a nonlinear controller is designed to improve the control accuracy of temperature. According to the model of Chylla Haase reactor, the differential geometry is utilized to achieve the exact linearization of input and output via diffeomorphism and state feedback. And then, by introducing an error tracking term and an integral term, this paper designs an asymptotic tracking controller with adjustable parameters to achieve the exponential decay of errors. The simulation results show that the proposed controller is superior to the cascade PID controller and fuzzy cascade PID in the tracking of set point and the anti interference.