Welded detail is the weak part of steel bridges. The fatigue damage of the welded joint is becoming one of key problems affecting the service safety of bridges under repeated vehicle loads. This study conducted static tensile and fatigue crack growth (FCG) tests of the base metal and weld joint of Q550E high strength steel. The FCG models of base metal and welded joint were established, and the effects of stress ratio on the FCG rate of welded joints of high strength steel were revealed. The coupled simulation method of FRANC3D and ABAQUS was performed, and the key influence parameters were determined by sensitivity analysis. The results show that the FCG rate parameter m increases with the increase of stress ratio. The FCG rate parameter lg C and the threshold stress intensity factor range decreases. The parameter m of butt weld specimen is about twice that of base steel. The threshold stress intensity factor range of weld joint is larger than the base steel and more sensitive to the stress ratio. The developed coupled simulation method can accurately predict the fatigue life of high strength steel welded joints. The specimen thickness and initial crack depth have a significant impact on the fatigue growth under high stress ratio.