The invention provides a saturation temperature determining and adjusting method, and relates to a production method of gas. The method comprises the following steps: when the circulation position of an oxidizing layer is high, the saturation temperature is decreased, the circulation position of the oxidizing layer is lowered by a distance less than or equal to the length of the oxidizing layer for each time; and when the circulation position of the oxidizing layer is low, the saturation temperature is increased, the circulation position of the oxidizing layer is lifted by a distance less than or equal to the length of the oxidizing layer for each time. Each time air and oxygen flow is increased or decreased, the circulation position of the oxidizing layer changes by a distance less than or equal to the length of the oxidizing layer. When the air and oxygen flow is increased, or the saturation temperature is decreased, or the air and oxygen flow is decreased, or the saturation temperature is increased, the circulation position of the oxidizing layer changes and is synchronous with circulation of the oxidizing layer; when the saturation temperature is decreased, discharged steam flow is increased; and when the saturation temperature is increased, the discharged steam flow is decreased. The saturation temperature determining and adjusting method has the advantages of high gasification efficiency, small fluctuation, reduced labor intensity and long service life of a furnace grate.