The invention discloses a three-phase flow separation device for natural gas wastewater. The three-phase flow separation device for natural gas wastewater comprises a circulating pump, a heating chamber, a separator and a solid-liquid separation device which are sequentially connected by circulating tubes to form a circulating system, wherein the circulating tubes comprise an upper circulating tube and a lower circulating tube; the separator is divided into an upper conical section, a straight section and a lower conical section, the outlet of the lower conical section is connected with a solid collector having a flotation function; the upper circulating tube is connected with the straight section of the separator; the lower circulating tube is connected with the lower conical section of the separator; an automatic washing gas-liquid separation device is arranged on the top of the separator. The three-phase flow separation device disclosed by the invention is simple in structure, convenient to use, low in equipment energy consumption, wide in treatment amount range and good in treatment effect, realizes large production scale for natural gas wastewater treatment devices and circulating utilization for natural gas wastewater, and has high environmental protection value and economic value.