The invention discloses a method for recycling valuable metals in waste lithium ion batteries. The method comprises the following steps: mixing waste lithium ion batteries with carbon powder, feeding into a rotary kiln for low-temperature reduction roasting, and controlling the roasting temperature to be less than 900 DEG C during low-temperature reduction roasting, so as to obtain a roasting product, wherein the amount of the carbon powder is not greater than 30% of that of the waste lithium ion batteries; mixing the roasting product with a slag former, so as to obtain a mixed material, wherein the mass of the roasting product accounts for at least 10% of that of the mixed material; feeding the mixed material into an electric furnace for smelting, so as to obtain an alloy with valuable metals and slag with CaO and SiO2. The method has the remarkable advantages of simple equipment, low investment operation cost, easiness in popularization, remarkable process energy consumption reduction, high valuable metal recycling rate and the like.