Based on the generalized gradient approximation of density functional theory, the geometric structure and electronic properties of the intrinsic Ti₃C₂ and Cu-, Pt-, Co-, Si-, F-, Cl- or Br-doped Ti₃C₂ are optimized, and the adsorption process of HCHO on the surface of the intrinsic Ti₃C₂ and doped Ti₃C₂ is calculated. The effects of adsorption energy, stability, DOS and doping on bond length were discussed. The results show that the adsorption energy of the intrinsic Ti₃C₂ crystal plane at the top site is the strongest, at −7.58 eV. The optimal adsorption sites of HCHO on various doping systems are Cu-Top, Pt-Top, Co-Top, Si-Hollow, Cl-Hollow, F-Bridge and Br-Hollow, respectively. Among the doped elements, anion (F, Cl, Br) doping at each adsorption site generally reduces the formaldehyde adsorption activity of the substrate; cationic doping (Cu, Pt, Co, Si) enhances the adsorption activity of the substrate for formaldehyde at most of the adsorption sites, indicating that the modification effect of anions on Ti₃C₂ is not as good as that of cations. The adsorption capacity of Si-doped Ti₃C₂ for formaldehyde was significantly improved. Compared with the intrinsic Ti₃C₂ crystal plane at the same adsorption site, the adsorption activity of HCHO was improved, and the highest adsorption energy was −8.09 eV.