Abstract: With the development and progress of economy, cobalt-based composite metal compounds have been widely concerned in the field of gas sensors because of their excellent electrochemical properties. For gas sensor, it has the advantages of high sensitivity, quick response, easy to carry, low price and so on. In this paper, the researchers prepared cobalt-based composite metal compounds with different morphologies in different ways are summarized, and their gas-sensitive responses to NO₂, ethanol and triethylamine are studied. The results show that cobalt complex metal compounds with different morphologies have important effects on the detection limit, working temperature, sensitivity and selectivity of gas sensors.