The invention discloses a niobium microalloying Mn-B series super-strength steel plate and a heat treatment process thereof and belongs to the technical field of heat treatment of materials. The process is characterized in that a plate blank comprises the following chemical components in percentage by weight: 0.18 to 0.38 percent of C, less than or equal to 0.6 percent of Si, 1.0 to 2.0 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.01 to 0.06 percent of Nb, 0.0005 to 0.0040 percent of B and the balance of Fe and inevitable impurities. According to the heat treatment process system, the austenitizing temperature is 880 to 930 DEG C, and after heat treatment is performed for 0.5 to 3 hours, water quenching is performed; and the tempering temperature is 190 to 280 DEG C, and the heat preservation time is 3 to 40 hours. The thickness of a finished steel plate product is 5 to 30mm, the finished steel plate product is excellent in mechanical property, the tensile strength reaches 1,100 to 1,400Mpa, the yield strength is 900 to 1,100Mpa, and the elongation percentage is 7 to 15 percent.