Abstract: In order to reduce the errors between the predicted field strength distribution and the actual distribution after the operation near the communication base station， a improved algorithm based on the traditional angle buffer algorithm is used to trace rays， and a field strength precise algorithm is put forward.The relation of the field strength is derived，by the establishment of three sets of coordinate systems，and considering the practical factors such as the“three petals” erection layout，downtilt，±45° polarization of the communication base station antennas.Considering antenna pattern and wave polarization plane rotation，amplitude and phase of field strength are calculated for each path.The exact solution is found through vector superposition for the field intensity of different paths.Two examples are calculated by using this algorithm，the error between the calculated results and the measured values is less than 4 dB.The algorithm and the program can be used for environmental impact assessment and the electromagnetic field strength prediction.