The invention discloses a honeycomb SnO2 semiconductor photocatalyst and a preparation method thereof. The photocatalyst is prepared from crystal tin tetrachloride, anhydrous sodium carbonate, acetone and absolute ethyl alcohol, wherein when the molar ratio of crystal tin tetrachloride to anhydrous sodium carbonate is controlled to be 1:6, honeycomb SnO2 is synthesized after heating is conducted for 2 hours at 540 DEG C by means of the solid phase synthesis method easy to operate. The preparation process is simple and operation is easy. After 0.3 g of prepared SnO2 is irradiated for 120 min under a 60 W fluorescent ultraviolet light, the reduction rate of 300 ml 50 mg/LCr(VI) can reach 87.8%, the catalytic effect of the honeycomb catalyst is obviously good, and hexavalent chromium in water can be removed at low energy consumption.