Abstract: Taking the 25Cr2Ni2MoV steel welded joint as the object, the low cycle fatigue experiments were carried out at different strain levels to obtain the low cycle fatigue strength characteristics, and the fatigue failure locations of the failed specimens were counted. Combined with the nanoindentation experiment and finite element inversion method, the mechanical properties of different regions of the welded joints were compared and the relevant parameters were obtained. Also, the stress-strain curve of the three regions including the base metal, the weld metal and the heat-affected zone was inversed. At the same time, the local axial strain distribution characteristics of the welded joint were obtained by finite element method, and the evolution mechanism of fatigue failure location of the welded joint changing with load level was revealed. The results show tht at low strain levels, the maximum axial strain of the welded joint is mainly concentrated in the base material near the heat affected zone（HAZ）, and the low cycle fatigue failure locations are also concentrated here. When the load level is medium, the axial strain of the base material and the weld near the HAZ is equivalent, and the low cycle fatigue failure position appears randomly in the two places. When the load level is large, the maximum axial strain appears at the weld center, and the fatigue failure position is also mainly present in the weld center.