The lead-free perovskites derivatives of Cs3Sb2X9 (X=Cl, Br, I) have been synthesized, but their photocatalytic properties are not explored. To evaluate the feasibility for the visible light catalytic performance, we calculate the structural, electronic, optical and charge transfer properties of Cs3Sb2X9, based on the hybrid density functional theory of HSE06 with the projector augmented wave potential. The results show the decrease of band energy gaps and the redshift of absorption edges from X=Cl to I. The absolute potential of the valence band maximum and conduction band minimum is determined to justify the feasibility of the photocatalytic water splitting or CO2 reduction. The calculated carrier mobilities reveal that the high electron mobilities of Cs3Sb2I9 are beneficial to the reducing powers for hydrogen generation and CO2 reduction. The present results indicate that Cs3Sb2I9 is appropriate for the photocatalytic water splitting to produce hydrogen or the CO2 reduction driven by the visible light.