In order to simulate the repair of rail gaps and cracks, a U-shaped groove was prepared on the U75V rail base material for laser filler wire welding repair. The optimized repair process parameters obtained were: laser power P=5 000 W, welding speed 500 mm/min, wire feeding speed 200 cm/min, defocus +20 mm, Z-axis lift 0.75 mm/track. The acicular martensite structure exists in the heat-affected zone of the weld after welding. After the high temperature tempering treatment at 600 ℃ for 1 h, the acicular martensite is transformed into tempered sorbite structure. After tempering, the tensile strength and hardness of the weld are close to that of the base material, and the friction coefficient is slightly higher than that of the base material, but it still meets the requirements of actual working conditions.