Abstract: Cracks were found on the supporting roller of a rotary kiln after hot installation. By means of macroscopic observation, chemical composition analysis, mechanical property test, metallographic examination and scanning electron microscope analysis, the causes of cracks on the supporting roller were analyzed. The results show that the cracks were caused by the defects formed by repair welding, and the formation and expansion of cracks were promoted by the large interference between the supporting roller and the supporting roller shaft, improper heat treatment process of the supporting roller, and unqualified yield strength.