In order to monitor indoor odour and improve the quality of life, this paper designs one MCU-based automatic odour detection system for indoor VOCs by taking the STM8S903K3 MCU as control element. The sensors were used to collect the concentrations of inhalable particulate matter (PM) and odour gas indoors. When the concentration of volatile organic chemical (VOCs) exceeds the set value, the system can automatically determine and emit an audible and visual alarm. This design has the characteristics of low power consumption, easy portability, and high sensitivity, etc. It is a convenient and practical odour detecting tool by detecting air odour in complex environments.