In order to evaluate the high cycle fatigue performance of laser weld joint with filler wire,the 2 ×10,6, high cycle fatigue strength of 0.7 mm thick laser weld joint with filler wire is evaluated by up and down method. SEM is used to analysis the fracture surface and fracture position. The results showed that the fatigue strength was 396.6 MPa. The fracture surface showed no precipitated phase. The crack source zone showed cleavage features,which mean the crack prolonged along the grain boundaries at early stage. The crack developing zone showed fatigue striations which became sparse with crack prolonging. Fracture zone feature was same with the tensile fracture surface which showed dimples and micro-holes features. The crack was originated from weld toe region on the top surface and prolonged along the thickness direction. During the propagation along the weld direction,the crack spread across the fusion line and in the weld zone and the adjacent base metal zone.