In the process of online monitoring of H₂S gas concentration, due to its strong adhesion, it is easy to occur pipeline adsorption, resulting in deviations in measurement results, especially in the process of trace H₂S detection. Therefore, it is particularly necessary to study the surface adsorption characteristics of H₂S gas pipeline materials. In this work, a set of online H₂S concentration measurement system is designed and constructed based on tunable diode laser absorption spectroscopy (TDLAS), and the measurement performance of the system is tested. On this basis, the adsorption characteristics of H₂S on the surface of stainless steel materials at room temperature are investigated. The experimental results show that the online H₂S concentration determination system has the characteristics of strong stability, low detection limit and high sensitivity, and can be used to achieve on-line continuous determination of trace H₂S concentration. After a series of experiments, it is proved that H₂S has obvious and stable adsorption effect on the surface of stainless steel material, and the adsorption capacity per unit area of H₂S on the surface of stainless steel material is 10¹⁴(PCS/cm²). The experimental results can provide a certain reference for on-line accurate measurement of trace hydrogen sulfide.