The invention relates to a low-cost Q550D steel plate and a manufacturing method thereof. The manufacturing method comprises the following steps: smelting molten iron in a converter, heating to 1250-1350 DEG C, adding scrap steel, adding aluminum to perform deoxidizing alloying by a single slag technique, and tapping while skimming, wherein the ladle needs bottom argon blowing operation in the tapping process; and after smelting the molten steel in the converter, refining the molten steel outside the LF (ladle furnace), adding manganese iron, ferroniobium, silicon iron, chromium iron and boron iron, carrying out RH vacuum degassing, adding ferrotitanium, sending the molten steel to a casting machine to carry out continuous casting, heating the prepared plate blank, and carrying out descaling, rough rolling, finish rolling, cooling, thermal straightening, heat treatment, shearing, hardening and tempering, sampling, inspection and finished product warehousing. By adopting the low-carbon component design, proper addition is adopted to enhance the hardenable element, thereby enhancing the steel cleanliness and optimally controlling the heat-treatment hardening and tempering technique to manufacture the low-cost Q550D steel plate.