Sulfur chloride analyzer is widely used for determination of chlorine content in products in petroleum, petrochemical, quality inspection and other fields. The uncertainty of the measurement results directly affects product quality. The uncertainty of instrument indication error was analyzed. It mainly includes uncertainty introduced by measurement repeatability, instrument indication resolution, the micro-sampler, value of standard materials. As a result, the uncertainty of the chlorine content of the sulfur chloride analyzer was mainly derived from the uncertainty of the standard material.