The utility model relates to the technical field of high-temperature saturated liquid sampling devices and particularly to a saturated liquid airtight sampling device capable of avoiding flash evaporation. The saturated liquid airtight sampling device comprises an inner piston cylinder, an outer piston cylinder, a hollow piston, an air compressor and a main pipe, wherein the inner piston cylinder is sleeved inside the outer piston cylinder; a cooling jacket is formed between the inner piston cylinder and the outer piston cylinder; the upper end of the inner piston cylinder is provided with an inner cylinder piston hole; the upper end of the inner piston cylinder is fixedly provided with an air compressor guide pipe, and the lower end of the inner piston cylinder is fixedly provided with a sample introduction guide pipe; the upper end and the lower end of the outer wall of the outer piston cylinder are respectively fixedly provided with a cooling medium outlet and a cooling medium inlet; and the hollow piston is sleeved in the inner piston cylinder and can slide. The saturated liquid airtight sampling device capable of avoiding flash evaporation is reasonable and compact in structure, convenient to use and capable of sampling saturated liquid at a high-temperature wellhead of an oil field and keeping the proportion of oil and water in a sample unchanged, so that the high-temperature liquid sampling accuracy and field operation safety are greatly improved.