Abstract: Based on the micro fracture mechanics, Q460 steel fillet welded joints were tested to study their fracture behavior. The constitutive relationship of weld metal materials were obtained through tension coupon tests. 11 smooth notch section tension specimens were used to calibrate toughness parameters of the void growth model (VGM) and the stress modified critical strain (SMCS) model η, α. A group of 5 fillet welded joints were tested to attain the load-deformation curves, which were simulated using the numerical method. The results of experimental study show that the fracture mode of lapped joints welded with E55-D2 weld metal was plastic. The analysis of the fracture parameters indicates that the chemical composition of welding materials will lead to differences in the fracture behaviour of the weld metals. In conclusion, an accurate numerical model for weld metal is developed and a reliable method is provided for the design of high strength steel welds and for the failure prediction of welded structures.