A control system for a plant is disclosed. According to this system, a model parameter vector of a controlled object model which is obtained by modeling the plant, is identified. A controller controls the plant using the identified model parameter vector. An identifying error of the model parameter vector is calculated, and the calculated identifying error is limited in a predetermined range. An updating vector is calculated according to the limited identifying error. The model parameter vector is calculated by adding the updating vector to a reference vector of the model parameter vector.