Abstract: Drilling fluid is very important for maintaining the stability of the hole wall in shale drilling. The mud cake formed by the fluid loss also plays a decisive role in protecting the reservoir. In order to study the influence of shale rock powder intrusion into low-solid-phase drilling fluids on the basic properties of mud cakes, the paper selects the siliceous shale powders in northwestern Hunan as the research object, and designs orthogonal experiments. In addition, the test results are analyzed using variance and range, which show that the content of rock powder is the main factor affecting the thickness of the cake. Besides, the main factors influencing the toughness of the cake are rolling time and the powder gradation. The mass fraction of 6% of the 200 mesh rock powder forms the thinnest mud cake after the rolling 6 hours. When the rock powder with a particle size of 150 mesh has a mass fraction of 6%, the toughness of the mud cake formed after rolling for 12 hours are the maximum. For the rock powder with a gradation of (200+100) mesh, the rock powder with 2% mass fraction forms the thinnest mud after rolling for 24 hours. When the gradation is (200+150) mesh, the rock powder with 4% mass fraction forms the greatest toughness of mud cake after rolling for 12 hours. The conclusion of the study has positive significance for the solid-phase control of the drilling fluid.