Abstract: To address the challenges of cleaning operations in confined and hazardous environments within natural gas transmission and distribution systems, such as natural gas separators with complex internal structures, limited operating space, and high operational risks, a multi-degree-of-freedom industrial robotic cleaning system driven by a differential-linkage hybrid mechanism is proposed. The system adopts a modular architecture integrating a rotary platform, differential gear assembly, and multi-linkage actuation structure, enabling high accessibility and flexible trajectory control of the spray unit within intricate internal geometries of industrial equipment. A kinematic and dynamic model of the core mechanism is developed to elucidate the geometric coordination between the end-effector posture and the main beam motion of the robotic arm, thereby providing a theoretical foundation for precise trajectory control. A collaborative control system based on the STM32F407 embedded platform is implemented, with wireless communication enabling remote operation and meeting the stringent safety and efficiency requirements of high-risk industrial scenarios. Experimental validation conducted on a prototype system demonstrates a cleaning coverage rate exceeding 90% and a repeatability error within ±1.5 mm, confirming good cleaning consistency and environmental adaptability. The results offer a practical engineering pathway for intelligent cleaning of industrial equipment, particularly those in sealed and hazardous environments, and contribute theoretical and technical insights into the design and control of multi-degree-of-freedom robotic cleaning systems for specialized applications in the oil and gas industry.