A fluorophotometrio method for the determination of the mioro quantity of sulfur in natural gas is reported. Organio sulfur compounds are first冲drogenolyzed at 900℃ by hydrogen with platinum catalyst to hydrogen sulfide, the volume ratio of the gas sample to the carrier gas being 1:10. The hydrogen sulfide formed is first absorbed by sodium hydroxide solution and then determined after the addition of meroury fluoresoein by measuring the extent of depression of the fluorescence. This method is found to be simple, facile and rapid. Each detemination requires about 20 minutes. Due to its wide measurement range and high sensitivity, amount of anlfar within the range of 0.02~1000 ppm may be soonrately determined. The peradntsge of average deviation is less than 15% for sulfur below 1 ppm level.