This is a national standard method for determining the total sulfur content in rubber materials using chemical fusion. The core of this method involves the high-temperature oxidation reaction of sodium peroxide with the rubber sample in an oxygen bomb, converting all forms of sulfur in the sample into soluble sulfates. After precipitation with barium chloride, the sulfur content is determined using the classical gravimetric method. It has a wide range of applications, covering products made from various common rubbers such as natural rubber, styrene-butadiene rubber, and nitrile rubber, as well as hard rubber, including sulfur present in inorganic fillers. Special attention must be paid to safety when using this method. Operators should have laboratory practical experience and strictly adhere to procedures, as sodium peroxide may ignite or explode upon contact with water. In addition to the analytical balance, oxygen bomb, muffle furnace, and crucible-type filter mentioned in the standard, modern instruments such as inductively coupled plasma optical emission spectrometry (ICP-OES) can also be used for quantitative analysis of sulfur in the solution after sample pretreatment to improve efficiency.