The choice of physical carrier sensing threshold affects the performance of the MAC (medium access control) layer protocol in multi-hop wireless networks. Previous research ignored the impact of the collisions correlated by ack frame and cumulative interference in determining the optimal carrier sensing range, and the collisions caused by hidden terminal were exaggerated to some extent. This paper presents a new analytical model to get the optimal carrier sensing threshold and transmit power while maximizing the network aggregate throughput. Through analyzing the cumulative interference in the network based on the carrier sensing threshold and transmit power, the channel rate and the number of the concurrent transmissions can be concluded. Additionally, four types of collision happened inside of the carrier sensing range and two types of collision contributed by the accumulative interference are proposed in this paper. Then, the channel activities can be modeled as a Markov chain that reflect the collision referred to above and the channel utilization by this Markov chain model is figured out. This paper investigates the impacts of the carrier sensing threshold and transmit power on the network aggregate throughput that determined by the channel capacity, channel utilization and the concurrent transmissions. Different from previous research, this research identifies the optimal carrier sense range without considering the collision from acknowledgement packet, accumulative interference and hidden terminals. The analysis proves that the aggregate throughput can suffer a loss, if the collision from acknowledgement packet and accumulative interference is not taken into account in determining the optimal carrier sensing range.