Cu2ZnSnS4 (CZTS) prepared by sol-gel spin-coating deposition was treated with post-sulfurization in a sulfur vapor atmosphere. The crystallinity degree of the CZTS could be significantly improved through post-sulfurization treatment. Granular structures of the CZTS as synthesized at a temperature of over 240 °C and treated with post sulfurization were obtained. The composition ratios of the as-sulfurized CZTS were close to the composition stoichiometry of CZTS with an electrical resistance of ~ 1.7 Ω cm. An as-prepared CZTS based solar cell shows an open-circuit voltage of 300 mV, and a short-circuit current of 2.48 mA cm-2.