Oxidative stress caused by pregnancy-induced hypertension syndrome significantly affects the health of pregnant women. Hydrogen sulfide is a typical gaseous signal molecule against oxidative stress, and it is of profound significance to develop a detection method. In this study, a stimuli-responsive hydrogel was constructed based on the coordination and bonding principle of metal ions and chitosan (CS) to realize the quantitative detection of hydrogen sulfide (HS). The chain of CS contains a large number of amino groups and hydroxyl groups, which can form the coordination structure with Cu, triggering CS to form a stable hydrogel. The hydrogel can be formed within about 5 s, which has the characteristics of rapid preparation. In the presence of target HS, the cross-linking agent Cu in the hydrogel can compete out, resulting in the collapse of the hydrogel and the release of the electrochemical probe. By detecting the concentration of the released electrochemical probe, the quantitative detection of HS can be achieved. The prepared hydrogel has a good linear relationship with the concentration of HS from 1 μM to 60 μm. At the same time, the hydrogel has good specificity and stability, and it can be applied to the detection of HS in serum samples.