Based on the apparent electrical variations anomalies in some typical earthquake examples, the relation between apparent electrical variation anisotropy and maximum principal stress from focal mechanism is introduced, the physical mechanism of this variation is discussed. The result shows that the apparent electrical variation is related with cranny ratio v, resistivity of water filled cranny ρ_f and resistivity ρ₀ of inherent framework,and coordinated with the earth-resistivity variation for dilatancy phase of focal region in DD model and that in loading process to rock(soil) sample.The main reasons of electrical variation are development of new-born crannies, connection of conductive channels and movement of conductive liquid near epicenter region during the late phase of strong earthquake preparation. The earth-resistivity observations in China have examined the information of this variation in deed.