In this paper, we focus on the performance analysis of the cognitive coexistence between Bluetooth and WLAN systems with sensing errors. The packet transmission rate and packet error probability are derived corresponding to the sensor operating points (consisting of the false alarm probability and the miss detection probability). Then, the optimization problem is established as maximizing the throughput of cognitive user with the constraint of the colliding probability with primary user. Simulation results illustrate that the proposed error analysis approach can obtain the optimal performance when considering the sensing errors. Moreover, the influence on the throughput of cognitive user caused by different sensor operating points is investigated by simulation.