The invention discloses a drilling fluid, which comprises bentonite, a high temperature resistance increased cutting fluid loss agent, a high temperature resistance viscosified fluid loss agent, a shale inhibitor, hollow glass microballoon and water. The drilling fluid has the advantages that the drilling fluid with low density possesses good stability, the high resistance capability can reach 180 DEG C, the drilling fluid possesses the effects of lubrication, collapse resistance and oil gas layer protection, no fluorescence is generated, no toxic pollution is generated, the environmental protection performance is good, and the preparation method is simple and easy to carry out.