In this paper, the 3-D Markov analytical model for cognitive radio networks of [1] are replaced by out proposed new 2-D Markov analytical model with considerable low complexity to evaluate the performance of Ad-Hoc Cognitive Radio Networks, and the theory mistakes of [1] are corrected. Compared with the existing 3-D Markov analytical model for cognitive radio networks, our approach has achieved the base performance with the low complexity. The numerical analysis and simulation show that the analytic model is accurate and compatible with the simulation results.