Abstract: In adaptive control systems, specifically in aircraft control systems, we often face the problem of identifying fast time varying parameters. Using broken line to approximate time varying parameter and based on the least squares principle, we have derived an identification algorithm which is simple for calculation with perfect accuracy. In this paper we have also done some simulations for control systems of antitank missile, ground to air missile and so on. The simulation results show that this algorithm not only can get good identification results for continuous fast time varyine parameters, hut also has enough accuracy for identifying parameters with discontinuous points oi second class in varying process.

Key words: Parameter identification, fast time varying system, covariance reset