Abstract: Casing galling accident occurred in one oil field, different opinions about casing galling cause are among the users and manufacturers. In order to find out the casing galling reason and the casing performance resisting to galling. An investigation based on material mechanical tests, thread gauging, and make up and break out tests are given in this paper. It is found that the casing galling reason is mainly due to bad casing quality instead of abnormal operation in oil field. The bad matching between pin and box, and thread joint′s poor surface treatment result inferior property resisting to galling.