The invention discloses high-temperature-resistant clay-phase-free hypotonic reservoir stratum drilling fluid, which can be absorbed quickly, has high inhibiting performance and causes little damage, which comprises the following components: 100 parts of sea water or fresh water, 0.2 to 0.5 part of fluid loss additive, 2.0 to 4.0 parts of high-temperature fluid loss additive, 0.2 to 0.5 part of extracting and cutting agent, 0.5 to 1.5 parts of high-temperature stabilizer, 0.5 to 1 part of water blocking agent and 10 to 233 parts of organic salt. The invention has the following advantages: (1) the drilling fluid can resist a temperature as high as 180 DEG C; (2) the rheological behaviour and water loss property of the drilling fluid are easy to control; (3) the drilling fluid can be well mixed with the fluid in a reservoir stratum with small damage to the reservoir stratum and is particularly suitable for hypotonic oil and gas reservoir; and (4) the drilling fluid can be applied to drilling completion operation of reservoir stratum sections of deep and medium-deep wells, particularly hypotonic reservoir stratums.