All-inorganic perovskite solar cells (PSCs) have gained significant attention due to their excellent photoelectric conversion efficiency and high stability. However, Pb-based perovskites are easily decomposed into toxic Pb compounds and are fatal to environment, which limit their further application. Despite the great effort carried out to substitute the Pb by a less hazardous element, lead-free perovskites still remain more unstable than lead-containing perovskites, and present lower performance as well. In this paper, Sn is used to partially replace Pb for obtaining all-inorganic tin-lead perovskite thin film, and salicylic acid is added for inhibiting the oxidation of Sn2+ to Sn4+, so as to achieve the goal of improving photoelectric conversion efficiency cells by a stable phase. The experimental results show that the photoelectric conversion efficiency of the device increases first and then decreases with the increase of the amount of salicylic acid from 2 mg·mL-1 to 6 mg·mL-1. Through the tests of SEM, XRD, XPS, it is found that the phase stability of the film is the best when the content of salicylic acid is 4 mg·mL-1. Compared with the device without salicylic acid, the short-circuit current density (Jsc) increases from 14.7 mA·cm-2 to 15.1 mA·cm-2significantly, meanwhile, the photoelectric conversion efficiency increases from 5.8% to 6.5%. In addition, the initial photoelectric conversion efficiency of the best device can still maintain 50% of the original efficiency after 5 d of storage in the air environment, which further proves that the addition of salicylic acid has a certain role in promoting the stability of tin-lead perovskite phase.