Cu2ZnSnS4 (CZTS) precursor thin films were prepared on a flexible Mo foil substrate via ZnS/Cu2SnSx stacked structure using successive ionic layer absorption and reaction (SILAR) method; the precursor thin films were annealed at 550 ℃ in sulfur atmosphere to obtain CZTS absorber layers. The chemical composition,crystallinity and surface morphology were characterized by EDS, XRD, Raman and SEM, respectively, indicating that the annealed films are highly crystallin and have compact morphology. In order to analyse the optical and electrical properties of the films, same processes were implemented on the soda glasses. Results reveal that the band gaps of the annealed films are 1.49 eV, the absorption coefficients are higher than 104 cm-1, and the carrier concentration as well as the electrical resistivity is suitable for fabrication of thin film solar cells. Flexible solar cells with a structure of Mo foil/CZTS/CdS/i-ZnO/ZnO: Al/Ag were fabricated by the above CZTS absorber layers, which demonstrated an efficiency of, 2.42%, the record efficiency of flexible CZTS solar cells as far as we know.