Due to tunable electronic and morphology structure, stable physicochemical properties and simple preparation, graphitic carbon nitride (g-C₃N₄) has emerged as an attractive candidate in the field of gas sensing. However, the gas sensing performance of pristine g-C₃N₄ is not satisfactory, due to the large band gap, high recombination of electrons and holes and low carrier mobility, leading to poor conductivity and surface activity. Therefore, multiple methods have been conducted to tune its gas sensing performance by providing more surface adsorption sites and improving surface activity. This review systematically represents the structure, synthesis methods and properties of g-C₃N₄, and summarizes their applications in gas sensors. Specifically, the modification, characterization, enhanced gas sensing performance and sensing mechanism are discussed in detail. In the future, related work should focus on the aspects of designing hierarchical and open structures, doping heteroatoms and building heterostructure. Moreover, π electron density control through carbon atoms injection or nitride atom vacancy and surface functional groups decorations are also proposed as potential strategies. This review is meaningful to promote the application of g-C₃N₄ in the field of gas sensing and development of novel strategy to enhance sensing performance.