The online monitoring of hydrogen sulfide (H2S) presents a critical advancement for environmental protection and public health, yet existing methodologies struggle to achieve on-site, on-line and highly sensitive detection in atmospheric conditions. This study introduces a novel approach employing ozone-enhanced photoionization ion mobility spectrometry (IMS) in conjunction with a time-resolved dynamic diluter (TRDD) for the efficacious identification of H2S within environments of high humidity, such as sewers. This method ingeniously addresses the challenge of distinguishing H2S in the presence of water vapor through a dual strategy of ozone oxidization pretreatment and TRDD injection. The strategic placement of ozone within the drift region significantly amplifies the sensitivity of the IMS detection, showcasing the method's superior sensitivity, stability, and humidity interference resilience. Notably, this technique achieves a detection limit for H2S at an impressive 2.5 parts per billion (ppb), maintaining a consistent relative standard deviation (RSD) of 2.5 % over three consecutive days. Furthermore, the approach effectively mitigates the effects of moisture, maintaining an RSD of 3.0 % despite a relative humidity (RH) increase from 22 % to 95 %. Applied to the on-site measurement of H2S in sewer systems, the method demonstrated all the aforementioned performance characteristics, marking it a promising way of high humidity environment H2S monitoring.