The invention discloses a chemical sewage filtering device. The device comprises a support mechanism, wherein the support mechanism comprises a sewage filter barrel and a sewage inlet pipe, a detachable drain pipe and three groups of supports are arranged at the lower end of the sewage filter barrel, a casing pipe is movably mounted on the detachable drain pipe, a threaded ring is arranged in a position, close to the casing pipe, of the detachable drain pipe, a valve is movably mounted in a position, close to the lower end, of the detachable drain pipe, a backwashing water pipe is fixedly mounted in a position, close to the upper end, of the sewage filter barrel, and a purified water drain pipe is arranged in a position, located below the backwashing water pipe, of the sewage filter barrel. To sum up, the device has the benefits as follows: the chemical sewage filtering device adopts a support mechanism and a filter mechanism, cleaning of a drain pipe is facilitated, filtered dirt canbe prevented from blocking the drain pipe, purified water can be prevented from being polluted again, thoroughness of sewage tretament can be guaranteed, and the device is simple in structure and convenient to use.