Abstract: Experimental study is made on the effect by sand on the anti-galling performance of the oil casing. Samples are taken from the connection of the 110 casing, and then successively subjected to the thread parameter measurement, the physiochemical property testing, and makeup/off tests under the standard conditions and the simulated sand condition.It is revealed via the analysis that spreading some sand on the coupling shoulder before makeup leads to moderate after make-off galling on the sealing surface and the shoulder, which proves that sand can produce an obvious influence on the galling resistance of the oil casing. Specifically speaking, it is the gathering of big sand particles on the coupling shoulder and the sealing surface that causes the galling. Accordingly it is suggested to optimize the design of the coupling shoulder structure for reducing sand gathering, and to strengthen the on-the-site operation management to prevent any foreign matters like sand from getting into the coupling.