Abstract: More serious cracking occurred at the simply supported end of large-span simply supported notched beam for a 8-story building after completion of its main structure in Shenzhen, Through cracks census of the damaged structure and ultrasonic testing of crack depth, it was found that the cracks could be divedes into several types, which were complecated and deeper, most of them were pass through ones, thus resulting in serious influence on the bearing capacity of the members.Based on analyzing the cause of the cracks and their influencing degree on the structural safety, the measures such as support treatment, enlargement of section and bonding steel plate etc were taken, by which excellent economic and social benefits had been got.