The invention relates to a universal joint for an oil and gas pipeline defect inner detector. A coupling shaft is split into two symmetrical half coupling shafts; universal joint components are connected without use of universal pin shafts; pin shaft-like structures are designed at the back ends of a left connecting block and a right connecting block; when the universal joint is used, the pin shaft-like structures of the connecting blocks are nested in pin holes of the half coupling shafts; sliding copper sleeves are arranged on contact surfaces of the pin shaft-like structures of the connecting blocks and the pin holes of the half coupling shafts so as to realize wearing reduction; the front ends of the connecting blocks are of fork arm structures; and flange connection pin shafts can be arranged at the front ends of the connecting blocks to realize coupling of the universal joint and other functional joints. The universal joint for the oil and gas pipeline defect inner detector has the characteristics of simple structure, convenient disassembly and assembly, high reliability and good capability of allowing a pipeline elbow to pass through and can be used for coupling various functional joints of different types of oil and gas pipeline detect inner detectors.