This paper deals with the design of an ultra­ local model control. The proposed approach is based on the estimation of the ultra-local model parameters using least squares resolution technique instead of numerical derivation technique. The closed-loop control is implemented through an adaptive PI in order to reject the influences of the dis­ turbance and noise output signais. Its main advantages are: its simplicity and its robustness with respect to the parame­ ter uncertainties of system. In this paper, it is processed to test the efficiency of the parameter estimation method com­ pared with the performance of numerical derivation tech­ nique. The method is applied to the water level control of a two-tank-system. Numerical simulations show that the gen­ erated desired trajectory is followed in an efficient way even with severe operating conditions.