The invention provides a biogas hydrogen production circulating system and technology for PTA sewage treatment. The system comprises: a PTA device, a settling tank, an anaerobic baffled reactor, a sedimentation tank, a biogas collection tank, a desulfurization adsorption device, a nitrogen-oxygen removal device, a cracking reactor, an alkaline washing tower I, a gas-liquid separator, a pressure swing adsorption device, a vapor heat exchanger, an alkaline washing tower II, a desalted water washing tower I and a desalted water washing tower II. According to the system and technology provided bythe invention, a sewage treatment unit in traditional technology is changed; sewage produced in a production process of the PTA device is subjected to biochemical treatment to generate biogas; methanein the biogas is extracted and converted into hydrogen; the hydrogen, together with the hydrogen converted from the released gas, is subjected to pressure swing adsorption to obtain high-purity hydrogen which is applied to a refining reaction of the PTA device; purchase of raw materials and energy is not needed, the operation cost of the PTA device is lowered, recycling of internal resources of the PTA device is realized, and an aim of energy conservation and emission reduction is achieved.