Abstract: In the past over ten years, the topic of intelligent control drawed a lot of attention and a number of possible implementation techniques were proposed. However the authors are convinced that the key to implement intelligent control is to employ qualitative models of controlled plants. In this paper we preliminarily discuss how to describe a qualitative model in mathematical language and propose a type of closed-loop qualitative control systems. Simulation results show that the behavior of a qualitative control system may properly approximate that of its quantitative counterpart. This implies that implementation of qualitative model based intelligent control is feasible.