Existing experiments have revealed that methylammonium lead iodide (MAPbI 3 or CH 3 NH 3 PbI 3 ) materials show favorable gas-sensing properties to reducing gas NH 3 and oxidizing gases O 2 and O 3 . The first step to effective gas-sensing by using semiconductor materials for gas-sensing applications is to recognize a target gas through gas-solid interaction. To explore the sensing mechanisms of perovskite materials to different oxidizing and reducing gases, the changes of skeleton structures of MAPbI 3 in reducing gas NH 3 and oxidizing gases O 2 and O 3 , adsorption energy, and charge transfer between gases and semiconductors are investigated through large-scale quantum dynamics simulations. By using three adsorption models, the differences and similarities of adsorption mechanisms of MAPbI 3 for gases NH 3 , O 2 , and O 3 are illustrated. These adsorption mechanisms are expected to provide new ideas for developing innovative sensing elements made of perovskite materials with stronger stability, high sensitivity, and high selectivity.