Abstract: In addressing the issue of sudden cracking in the crane block ring during normal operation. This study employs a comprehensive array of analytical techniques including chemical composition testing, Vickers hardness testing, fracture analysis, metallurgical organization analysis, and cross-section energy spectrum analysis. The objective is to ascertain the root causes behind the cracking phenomenon. Analysis of the results reveals that while the chemical composition, Vickers hardness, and presence of inclusions near the crack conform to standard requirements. Significant folding defects are observed on the surface of the weld bulge, along with the presence of oxides and sulfides. Based on the crack characteristics, it is determined that the weld fracture is of brittle nature. That attributed to subpar welding quality resulting in an abundance of oxygen（O）, sulfur（S）, phosphorus（P）, and other elements at the weld site, consequently facilitating the formation of weld cracks.