Abstract: LO-CAT Ⅱ sulfur recovery unit commissioned successful in October 2009. During the process of actual operation, the generated sulfur particles had small diameter and high viscosity sometimes, which made it difficult to gather into larger particles. The small sulfur particles could pass through the filter cloth and be discharged with the flushing water of filter cloth, which would increase the burden of sewage treatment. It was found that the vertebral body of the reactor had a different degree of sulfur accumulation during the process of reactor maintenance. The sulfur recovery reactor cone jammed frequently for 20 times, which affected the normal operation of the plant seriously. Aiming at the blocking reasons of reactor cone of LO-CAT Ⅱ sulfur recovery unit, the comprehensive analysis was carried on. By adopting these measures such as adjusting the amount of each chemical reagent and addition speed, filter reconstruction, increasing cooler, the sulfur blockage problem of the reactor cone for sulfur recovery unit was solved.