The function and structure and the architecture of sensor network based on ZigBee/802.15.4 standard for forest monitoring are designed in this paper. According to the features of forest monitoring, the sensor nodes based on CC2520 and low power consumption chip MSP430F5437 and the coordinator Combing with ARM are designed which realize the energy control in physical layer. With the wireless sensor network nodes based on ZigBee/802.15.4 standards and leading distribution into multidimensional scaling techniques, it improves the location algorithm. By analyzing radio propagation path loss model and CC2520 chip character, it gets the relationship between transmission power, RSSI, LQI and the distance of the nodes using Piecewise linear approximation method. It also gets the relationship between transmission power, error rate and the distance of the nodes by further optimization. It establishes a cross-layer energy optimization algorithm based on the distance of nodes, RSSI and LQI for the situation of fewer communication and lower demands of hardware.