Abstract: The system throughput and the message transmission delay influenced by the channel access parameters under various channel access rules is studied in this paper. The analysis is based on the model of channel access state transition for VHF air-to-ground data-link and CSMA matrix analysis method. The channel access parameters include the updating rate of report, the message length, the detecting density, the date rate of data-link, the coverage of remote ground stations, the number of aircrafts operated by remote ground station. The simulation results show that these parameters have significant effects on the performance of VHF air-to-ground data-link. At the same time, valuable conclusion is obtained from the simulation results.