The invention relates to a method and a device for dissolved absorbing hydrogen sulfide in a liquid. The method comprises the following steps of: heating a liquid containing liquid-phase hydrogen sulfide to 50-90 DEG C, and introducing an inert gas for 1-3 hours, wherein the flow rate of the inert gas is 10-100 ml/min; and detecting the hydrogen sulfide in the displaced gas. The device for absorbing the dissolved hydrogen sulfide in the liquid comprises a liquid collection bottle, a gas absorption bottle, a one-way valve assembly, a capacity detection and monitoring instrument and a Hall element, wherein the liquid collection bottle is in a series connectiong with the gas absorption bottle through the one-way valve assembly; and the capacity detection and monitoring instrument and the Hall element are respectively arranged in the liquid collection bottle and the gas absorption bottle. The invention can correctly absorb the dissolved hydrogen sulfide in the liquid and accurately calculate the content of the hydrogen sulfide in the liquid, and provids a precise data base for the selection of corrosion resistant alloy in the environment containing the hydrogen sulfide as well as the comparison of indoor anticorrosion effects of different alloys in the environment containing the hydrogen sulfide; and in addition, the invention can also provide a data base for treating sewage containing the hydrogen sulfide.