Defects in perovskite film are sources of charge recombination centers, which is detrimental to the performance of perovskite solar cells (PSCs) [1-3]. To decrease the density of defects, dodecylamine (DAM) and dodecylic acid (DAC) which contains –NH2 and –COOH groups, respectively, are utilized as additives to prepare methyl ammonium lead iodide (MAPbI3) perovskite films. Meanwhile, 12-aminolauric acid (ALA) which consists both –NH2 and -COOH at two ends of the alkyl chain, was also utilized for comparison. The passivation effects of these molecules on the properties of the MAPbI3 films and the performances of the corresponding PSCs were studied herein. The results show that introduction of –NH2 and -COOH groups led to decreased binding energies (EB) of Pb (4f5/2, 4f7/2), indicatinfg that both the Lewis acid groups act as electron donors, coordinating with the undercoordinated Pb2+; therefore, the EB of Pb decreased after accepting the electrons. The analyses also show that the treatments of the molecules result in higher PL intensities, longer TRPL lifetimes, smaller dark currents and defect densities. Comparing the passivation effects of the three molecules, ALA is more significant, which is attributed to the synergistic effects of the -NH2 and –COOH groups at the ends of an ALA molecule, as the model shown in the attached Figure 1(b). On the other hand, DAM and DAC have less passivation ability because the passivation can only be carried out by group of –NH2 (DAM) or –COOH (DAC), which oritation is demonstrated in Figure 1(a). The experimental results show that the PCEs of the PSCs can increase from 18.50% to 19.96% by the passivation of ALA; furthermore, the stability of the cell can also be improved.