The invention discloses low-brittleness 700MPa-level automobile beam steel and a manufacturing method thereof. The low-brittleness 700MPa-level automobile beam steel comprises the following chemical components in percentage by mass: 0.05-0.07% of C, less than 0.1% of Si, 1.45-1.75% of Mn, less than 0.012% of P, less than 0.005% of S, 0.020-0.070% of Al, 0.035-0.050% of Nb, 0.08-0.1% of Ti, less than 0.005% of N and the balance of iron and unavoidable impurities. The low-brittleness 700MPa-level automobile beam steel is manufactured by the steps of molten iron desulfurization, converter smelting, vacuum treatment, continuous casting, slab checking and cleaning, slab heating, hot continuous rolling, laminar flow cooling, coiling and finishing. The low-brittleness 700MPa-level automobile beam steel disclosed by the invention has high strength, and the weight reducing effect can reach 10-25% in frame design; with good formability, the low-brittleness 700MPa-level automobile beam steel is suitable for the processes of stamping, rolling, bending and the like; with low-temperature toughness, the low-brittleness 700MPa-level automobile beam steel is suitable for the transportation in cold regions.