La1.8M0.2NiO4 (M=Na+, Sr2+, Ce3+) perovskite-like catalysts were prepared by citric acid complexation method. XRD, BET, FT-IR, SEM, XPS, H-2-TPR, O-2-TPD, MS-Soot-TPR, MS-NO-TPD and catalytic activity measurements were carried out to investigate the effect of A-site substitution on structure and catalytic performance for simultaneous removal soot and NOx. The characterization results show that La1.8M0.2NiO4 catalyst has high concentration of oxygen vacancies, more surface active oxygen, more trivalent nickel ions and better reducibility, which determines its better catalytic performance. The introduction of low valence cations at the A site significantly reduces the characteristic combustion temperature of soot and effectively promotes the reduction of NOx by soot. La1.8Sr0.2NiO4 catalyst exhibited the best soot removal performance with T-i 331 degrees C and T-m 473 degrees C, while La1.8Na0.2NiO4 catalyst showed the highest NOx conversion of 90%. Based on in situ DRIFTS and other characterization results, a possible mechanism for simultaneous removal of NOx and soot was proposed.