Abstract: The calculation method of explosion relief area for lithium-ion battery thermal runaway (LIBTR) environmental structures is still unclear. Using an 8L cylindrical explosion test device, five discharge diameters of 10.5mm, 15mm, 21.2mm, 30mm and 60mm were set to simulate the explosion relief law of LIBTR environmental structures. The results show that the explosion relief pressure Pred of the gas (BVG) released by thermal runaway of lithium-ion batteries is higher than the Pred of the BVG-graphite powder mixture, and the influence of solid particles ejected by thermal runaway can be ignored; Pred decays exponentially with the increase of the discharge diameter and grows logarithmically with the opening pressure Pstat of the explosion relief device; combined with the specifications, the calculation formula for the explosion relief area of lithium-ion battery structures is obtained, and the commonly used pressure relief ratio C is given as 0.11. The research results provide a reference for the explosion relief of lithium battery environmental constructure.