| The electronic structures and reactive activities of metal dopants (M = Mo, Al, Co, Fe, Au and Pt) incorporated N4 centers in graphene sheets (M-GN4) are investigated using first-principles based on density functional theory. It is found that the metal dopants in GN4 sheet exhibit different stabilities. The doped metal atoms (Mo, Al, Co, Fe and Pt) have more stability ( 6.0 eV) than that of the Au dopant, and these dopants provide the transferred electrons to GN4 sheet and exhibit the more positively charged, which would regulate the adsorptive property of gas molecules. Compared to other M-GN4 substrates, the Mo-GN4 and Al-GN4 sheets exhibit the high sensitivity for the adsorbed O2, and the adsorption of CO and O2 have smaller energy difference on Co-GN4 (or Fe-GN4) sheet. Besides, the electronic structures and magnetic properties of M-GN4 systems can be effectively modulated by the adsorbed gas molecules.