The invention discloses a manufacturing method of a high-toughness hot-rolled plate coil for a welded gas cylinder. The hot-rolled plate coil comprises the following components in percentage by weight: 0.045-0.095% of carbon, 0.20-0.28% of silicon, 1.30-1.50% of manganese, less than or equal to 0.015% of phosphorus, less than or equal to 0.005% of sulfur, 0.020-0.050% of niobium, 0.015-0.030% of titanium, 0.035-0.040% of aluminum and the balance of iron and trace impurities; and the manufacturing technology of the hot-rolled plate coil comprises the steps of smelting, pretreatment of molten iron, refining in an LF furnace, continuous casting, heating, rolling and coiling. In the method disclosed by the invention, the three key links from composition design, rolling to smelting are strictly controlled; and the yield strength of the obtained hot-rolled plate coil is 350-500MPa, the tensile strength is 510-600MPa, the ratio of the yield strength to tensile strength is less than or equal to 0.80, the Charpy impact energy at -20 DEG C is 150J, and the Charpy impact shear area (SA%) at -20 DEG C is 100%.