The invention discloses a pipeline bio-membrane reactor with a detachable inner body. The pipeline bio-membrane reactor comprises a shell, the inner body and two double-layer water distributors, wherein the shell comprises a shell casing pipe and a connector, the inner body comprises an annular pipe section and a clack-shaped pipe section, the two double-layer water distributors are respectively arranged at the two ends of the inner body, and the inner body and the two double-layer water distributors are exactly right nested in the shell. The pipeline bio-membrane reactor is suitable for research of pipeline biological membranes in water supply pipe networks, uniform in water distribution and controllable in hydraulic conditions; after the biological membranes are cultured, the sampling and research of the biological membranes are carried out in the detachable inner body; the pipeline bio-membrane reactor is simple, convenient, fast, compact in structure and low in cost.