Mechanical defects are incurred routinely in the coiled tubing (CT), and can have a first order influence on fatigue crack development. Failures of the CT can significantly impact operations and in a worst case can lead to the loss of a well. This paper developed the new non-contact CT assessment system with the new inspection method, which is suitable for the detection in-service and new coiled tubing. This paper proposes a new micro-magnetic detection technology for rapid detection in-service coiled tubing. The method is based on a high precision fluxgate sensor that measures the magnetic field changes in the geomagnetic field, without needing external magnetization and demagnetization to identify the location of the defect. We use iron base amorphous alloy to make the smallerfluxgate sensor. This method is effective in assessing the early damage and developed defects. Eddy current lift-off technique is used for the gap measurement and design ovality detection algorithm. The ovality is obtained through calculation of the software. The optical distance measure sensor measures down to the length of the coiled tubing. The test tool is designed and produced and can be installed and removed fast. 2D imaging is achieved and features the shape of defect. This system is available for various CT diameters. Data acquisition software real-time display flaws curve and the detection imaging. The tool can realize non-contact, measure wall thickness, diameter, ovality, and can fast nondestructively test in-service coiled tubing. The resolution of the testing instrument is 1 mm. It is easy-operating and time-saving, and has the maximum measuring velocity of up to several meters per second. Detection results are close to accurate location of prefabricated corrosion defects through inspection CT test sample. However, as a comparatively new test method, it still has a large room to be improved. Micro-magnetic measurement signals are weak, and its amplitude is small and unperturbed by the environment. Inspection of in-service coiled tubing still need to improve and develop.