Toxic and harmful gas is a critical factor for the quality and safe production of coalbed gas and natural gas. Meanwhile, it is uncommon for systematic study on H2S and SO2 as well as their toxicology and harms in coalbed gas and natural gas. This paper studied the toxicity and its mechanism of H2S and SO2, carried research on the distribution of H2S and SO2 in coalbed gas and natural gas and related major problems, and analyzed and discussed the causticity and toxicity of H2S and SO2, along with related accidents, in exploration and the mining of natural gas and coalbed gas. The results strongly recommend that the content of H2S and SO2 be considered in coalbed gas areas for exploring and mining. Initial research has suggested that the safety threshold value is approximately 0.0013% for H2S, and 0.036% for SO2. Advanced research is in demand. In addition, the paleogeography deposition environment during the coal forming can serve as an index for selecting coalbed gas areas to explore and mine.