?In order to explore the loading conditions and the fatigue life of dangerous weld area of STS Cranes’ bracing tube sealing plate, typical load cases of the 65t/60m STS crane has been analyzed . The loading condition of bracing tube sealing plate weld has been studied through calculating the fatigue load amplitude of the horizontal bracing tube on the door frame. Main S-N curve method has been applied to calculate the weld structural stress, and the fatigue life of dangerous position has been analyzed.The results show that the maximum Von Mises stress appears at the end of sealing plate and node board of fillet weld toe. The weld fatigue life of the dangerous parts on sealing plate cannot meet the safety requirements of STS Cranes’ 30 years service life.