Many of the NDT methods used for casing, tubing, drill pipe and line pipe are applicable, with some minor modifications, to CT. This article describes the requirements of an ideal in-service inspection. This paper presents a new wall thickness and ovality measuring method engineered for reliable field use. This method based on flux gate testing technology discussed in this paper .This method not only will detect internal flaws and the density of micro-cracks, but also wall thickness measurements will be made. This paper discusses the development of this new method, the detection of eddy current testing program is used in coiled tubing ovality measurements. The key technology is the production of amorphous alloy core. Using this method measure diameter, wall thickness and ovality of CT, is currently being developed.