In order to deploy short-range wireless communication devices in the pri-mary transformer substation, a Maximum Inner Product (MIP) Method is proposed to extract the path-loss parameters in 110kV and 220kV primary transformer substations. The maximum inner product of the testing data is calculated to find out the loss index n and the standard deviation σ, and then the path-loss models can be set up. By comparing the MIP with Minimum Mean Square estimation (MMSE) and Cumulative Sum (CUSUM), MIP can match the measured values best. In order to apply the MIP path-loss model, under the initial signal to noise ratio (SNR) at 5 dB and 10 dB, a ZigBee simulation system is con-structed to validate the situation that bit error rate (BER) varies with distance. And the Zig-Bee devices with 5 units are tested in a 220kV primary transformer substation. The result of the test proves that the path-loss model is ac-curate.