Abstract: Although research on fatigue properties of welds under normal stress loading conditions was conducted widely by scholars world widly, little study on shear fatigue resistance has been done. A number of shear fatigue tests are conducted on a high frequency fatigue machine. For the tests, side fillet welded and front fillet welded specimens are used. The test results show that the discreteness of the fatigue strength is fairly great. The shear fatigue strength of Q345B longitudinal fillet welded connections under two million times of loading is greater than the corresponding strength calculated according to the GB 50017-2017 code. The two curves match well. The fatigue strength of the front fillet weld is higher than those given by the codes of many countries. The fatigue performance of the front fillet welds is better than that of the side fillet welds. The fatigue failure cracks of the front fillet weld go through the weld. Meanwhile, cracks of side fillet weld extend from the weld toe to the heat affected zone. The results show that the current Chinese standard evaluation of fillet weld shear performance is conservative, but the fatigue performance of side fillet weld is more consistent with the recommended curve.