Abstract: A special H type component in welded steel bridge structure is semi experientially analyzed and the influence of welding residual stress is considered simultaneously. Based on the hypothesis of critical crack size and on the classification of design stress, the stress intensity factors of H type component are derived.The critical crack size of 2a_C is 60mm, the stress intensity factors of the base and welded seam in H type component are K ^B_I=1.12 (α +β₁)σ_sπa_C and K^W_I =1.12 (α +β₂)σ_s πa_C respectively.