Abstract: The hydraulic support column cracked in the middle cylinder after only 7 months of use. The causes of cracking of the middle cylinder were analyzed by analyzing the chemical composition of the sample, optical metallographic structure observation, tensile experiment, impact test, etc., and SEM fracture observation. The results show that the strength of the material does not meet the national standard, which will adversely affect the cracking of the cylinder block. The presence of microcracks in the inner hole overlay layer and its welding heat affected zone and penetration of welding metal is the most important cause of cracking of the cylinder during use.