The invention relates to the technical field of welding and post-welding heat treatment, and provides a heat treatment method capable of improving the plasticity of a high-static-toughness medium manganese steel laser welding joint. According to the heat treatment method, high-static-toughness medium manganese steel comprises the following chemical components in percentage by weight: 0.05-0.45wt.%of C, 4.50-8.00wt.% of Mn, 0.01-2.50wt.% of Si, 0-3.00wt.% of Al, no more than 0.02wt.% of P, no more than 0.02wt.% of S, 0-0.02wt.% of Nb, 0-0.30wt.% of V, 0-0.30wt.% of Ti, and the balance of Fe and inevitable impurity elements. The method comprises the following steps: carrying out heat treatment on the welding joint after welding, wherein a vacuum heat treatment furnace is adopted, the heat treatment temperature is set to be 650-750 DEG C, a workpiece is put into the furnace after the set temperature is reached, the penetration protecting operation is performed for 5 +/- 2 min, and the heat preservation time is 10 min to 3 h; and taking the welding joint out of the furnace after the heat preservation time is reached, and carrying out air cooling to the room temperature.