With the rapid leap in economic and social development and information technology, wireless sensor technology has penetrated into all aspects of people's lives, the field of application relates to the military, environmental protection, industry and agriculture, and transportation management. We try to apply the theory of double clocks control to the CSMA protocols, setting the probability of sending packet and the probability of sensing channel to improve system performance. Through modeling analysis, the proposed double clocks two-dimensional probability CSMA with the function of monitoring can decrease the system idle time, making the channel resource highly use; the analytical results and simulation results show that the theoretical analysis are consistent with the simulation experiments and realize the function of monitoring.