In accordance to the testing requirement of the flaws on rail tread,the laser- electro magnetic acoustic (EMA) testing system based on fiber conduction is es tablished to test the flaws on rail tread.The system can generate ultrasonic surface wave on rail tread by laser pulse.It is known that shear wav e component which can be received by EMA technology can be produced due to the mode conversion when the ultras onic surface wave is transmitted through the surface crack.The system can precisely test the flaws by inspecting the rail.T he experimental research shows that this system can effectively test the flaws on rail tread,and has advantage s of non-contact,flexible structure and high sensitivity.