Abstract: The traditional inspection methods for buried pipelines require extensive excavation and exhibit limitations in terms of precision, adaptability, and reliability. To address this issue, an adaptive ultrasonic internal inspection robotic system for D1016 mm pipelines based on phased array ultrasonic technology was developed in this study. Based on the principles of phased array ultrasonic inspection, a high-precision self-aligning modular detection device was designed, incorporating a multi-floating structure to ensure tight coupling between the probe and the pipe wall, simultaneously employing a weld seam positioning module to enable precise identification and localization. To improve adaptability under various working conditions, a wheeled pipeline robot with a self-adjusting wheel structure was designed to enhance operational performance in complex environments. In response to control and communication challenges, a wireless control system was established using the robot Ethernet and controller area network (CAN) bus for efficient coordination, enabling modular design and distributed control. Results from dedicated loop tests and defect detection experiments show that the robot can achieve stable operation within the pipeline, with a defect detection rate of 100%. The inspection efficiency significantly surpasses that of traditional methods, providing an efficient and reliable solution to substantial engineering application value and ensuring comprehensive technical and equipment support for the safe operation of pipelines.