The model-free adaptive control (MFAC) approach of nonlinear systems based on linearization of tight format is applied to multiple-effect evaporator contro1. The controller design is based directly on pseudo-partial-derivatives (PPD) derived on-line from the input and output information of the multiple-effect system. The simulation examples prove its validity and stability for nonlinear systems of multiple-effect evaporator by using MATLAB software. The performance outperforms traditional PID controller.