Solid phase control is important to the maintenance of drilling fluid properties. Through the laser particle size measurement of the rock powder from diamond drilling of hole No.3 (WFSD-3)in Wenchuan earthquake fault zone scientific drilling, this paper analyzes the rock powder particle size distribution to provide the basis for the scientific design of geological core drilling solid control equipment and reasonable configuration of geological core drilling solid control system, and ultimately achieve the aims that the content of harmful solid in drilling fluid is effectively controlled to stabilize the drilling fluid performance.