The wireless sensor network is a new hot spot in the field of wireless network. Compared with other network technology, wireless sensor network has less communication protocols, mainly including Wireless HART, ISA100.11a, IEEE1451, and ZigBee/IEEE802.15.4. IEEE802.15.4 was designed for short-range, low-complexity, low-power, low-rate and low-cost wireless network which provides two-way wireless communication technology [1]. In this paper, the performance of IEEE 802.15.4 is analyzed based on OPNET simulator. The simulation result indicates the influence of ACK mechanism and different network load on the system performance,i.e. end-to-end delay, packet reception ratio and throughout of node, which provides an important theoretical basis for the construction of actual network.