Abstract: To address the problem of internal inspection of complex pipeline welds, an omnidirectional multi-joint internal inspection robot was designed, which was suitable for pipelines ranging from 200mm to 400mm in diameter. It could smoothly pass through T-shaped branches and vertical pipelines. The STM32 was chosen as the main control chip, along with the design of power supply circuit, motor drive circuit, and gimbal control circuit, forming the internal inspection robot platform with the aid of reduction motors and steering gear. By adjusting its posture, the robot platform could adapt to various pipeline shapes and structures. Equipped with a visible light camera, a lidar, and an IMU, the robot conducted internal inspection, scanning, and modeling of complex pipe networks. It marked weld defects, extracts features, and performs evaluations. Experiments in pipeline scenarios verified that the pipeline inspection robot possessed excellent obstacle-crossing performance and wall-climbing ability, providing platform technology support for complex pipeline weld inspection and safe operation of pipelines.