The invention relates to a detecting device for total sulfur content in natural gas and a detecting method thereof. The detecting device comprises a gas delivering pipeline, a pipeline valve, a vaporsaturator, a hydrolysis reactor and a hydrogen sulfide measuring device, wherein the pipeline valve, the vapor saturator, the hydrolysis reactor and the hydrogen sulfide measuring device are sequentially arranged on the gas delivering pipeline, the pipeline valve is connected with a gas inlet of the gas delivering pipeline, a gas outlet is formed in the hydrogen sulfide measuring device, the hydrolysis reactor is filled with an organic sulfur hydrolyzing catalyst, and the hydrolysis reactor is connected with a heater. By the aid of the detecting device, sulfide in the natural gas can be hydrolyzed into hydrogen sulfide, then the total hydrogen sulfide content in a composite sample can be measured by the hydrogen sulfide measuring device, and the total sulfur content in an original naturalgas sample can be obtained by calculation. The detecting device is simple in structure, simple and safer to operate, low in cost and high in precision, overcomes the deficiency that the semiconductorlaser absorption spectrum technology cannot be used for online measurement of the total sulfur content in the natural gas and provides a novel effective measurement means for the total sulfur contentin the natural gas, and the detecting method is mild in condition.