Hongyakou coal exploration project in Luoping County of Yunnan Province is located near the fault zone. Influenced by multiphase tectonic geological processes, parallel thrusts, lateral strike-slip faults and a small amount of normal faults developed. There are serious deformations by extrusion, large strata inclination and even with local upright to inverted and broken strata. According to the low drilling efficiency and frequent accidents caused by severe upper leakage and drilling to the fault fracture zones and coal-bearing strata, the researches and tests were made to explore the mud suitable for complex strata drilling of coal exploration in this coal mine.