SPV490Q steel is a low alloy high strength structural steel plate used in the manufacture of oil storage tank. To improve the comprehensive performance of SPV490Q steel plate and reduce manufacturing costs, direct quenching technology has been developed as revolutionary plate manufacturing technologies in recent years. Effect of direct quenching on microstructure and mechanical properties of high performance SPV490Q steel plate has been studied. The direct quenched (DQ) steel plates are rolled at different finish rolling temperatures, and their microstructures and mechanical properties are compared with those of reheat quenched (RQ) steel plate. The optical microstructure of the DQ steel shows deformed grains elongated parallel to the rolling direction, while complete equiaxed grains are visible in RQ steel. The transmission electron microscope (TEM) microstructure of the DQ steel shows refined lath martensite with high density of dislocations. The findings indicate that the application of the direct quenching process to low-carbon alloy steels contributes to the production of steel plates with excellent strength and toughness.