Abstract: WiFi electromagnetic wave penetration wall capability influences directly the effect and quality of communication. Combining electromagnetic characteristics of brick wall，we analyze theoretically the propagation characteristics of WiFi electromagnetic wave in the brick wall， the relationship between derived WiFi electromagnetic wave through the wall thickness and average power flow density. Examples and images of rgy transfer are given. Results show that WiFi electromagnetic waves can penetrate brick wall. In the process of transmission，the signal energy is gradually attenuationbutless attenuation. Therefore，the brick wall has little impediment of WiFi communication connection.

Key words: WiFi electromagnetic wave, brick wall, average power flow density, attenuation