Although smart antenna will be intro-duced in the third generation mobile communicationfor its great improvements on the capacity, it is not asimple task to commercialize this technique to prac-tical fields, mainly because the overall procedure re-quires an enormous amount of computation. For mostadaptive processors, the calculation burden can be at-tributed to the calculation complexity required by thealgorithm at each iteration and the iteration rate re-quired by adaptivity of system in time-varying chan-nels. The presented paper presents an analytic solu-tion for estimating the tracking capability of the Re-cursive Least Square (RLS). This approach is formedby the simulation results.