For the products with less [H] content, the effect of the traditional smelting process of arc furnace+LF furnace on reducing the gas content in steel is not obvious which cannot meet the requirements of the products. A 25T-VD vacuum refining furnace is specially equipped in the smelting workshop of a company. The degassing parameters and process of the 25T-VD vacuum refining furnace are optimized according to the changes of gas content in molten steel in each stage of steelmaking and casting process, the goal of gas content in steel [N]≤60×10-4 %, [H]≤2×10-4 %, [O]≤30×10-4 % was finally achieved, which not only guaranteed the quality of the product, but also reduced the time of dehydrogenation in the later stage, to optimize the production process, save energy, shorten the production cycle.