A nonlinear model of a liquid level process is obtained on the analysis of its nonlinear characteristics, finding the basis of its nonlinear process parameter correction and a nonlinear system control strategy based on single chip computer is presented. By measuring the liquid level and flow rate, two nonlinear process parameters of the liquid level process, the amplification coefficient and time constant under different load are calculated according to the basis of the nonlinear process parameter correction. Then the control signal is calculated and the system is run according to the nonlinear system control strategy. A test results is given and it shows that the nonlinear system control strategy is better then the linear system. The maximum overshoot is reduced by 16%.