The invention discloses a heat treatment technology for improving high-temperature tensile ductility of Ni-Fe-Cr based deformation high-temperature alloy. The technology includes the steps that heat preservation lasts for 0.5-2h within the temperature range of 1050-1200 DEG C for performing solution treatment; the temperature is lowered to 20-150 DEG C below a gamma' phase precipitation temperature from the solution temperature at the speed of 0.1-20 DEG C/min, and air cooling is conducted to an indoor temperature after heat preservation lasts for 0.5-4h; and heat preservation is performed for 4-30h at the temperature 150-350 DEG C below the gamma' phase precipitation temperature, and air cooling is conducted again to the indoor temperature. According to the heat treatment technology, the method with high-temperature solution, slow cooling and low-temperature aging combined is adopted, the grain size of an obtained alloy structure is moderate, a bent sawtooth crystal boundary is formed among grains, and M23C6-type carbide is evenly distributed on the crystal boundary; and the crystal boundary has a good reinforcement effect under the high-temperature condition, and the high-temperature tensile ductility of the alloy is high.