Abstract: Traditional caliber method for Pre-commissioning pipeline has shortcomings such as long caliber period, high manpower and material resources consumption and low reliability. To solve this problem, a new smart calibre detector for Pre-commissioning pipeline has been developed. The main mechanical part of this device consists of cylinder, rubber cup, deformation probe arm and odometer wheels, while the main electric part is composed of recorder, battery array, marker and deformation sensor. This smart calibre detector, mainly using air compressor as power source and operating under the environment of non-back pressure in pipeline, has to overcome problems like loss of detection data and signal distortion caused by unsteady operation. The practical application in field shows that this device can quickly find out, quantify and locate the deformation points in pipe in a short time, and thus greatly reduce the construction period and provide a scientific basis to the pipeline's acceptance.