Steel bar diameter detection device and detection method for constructional engineering detection

The invention relates to a steel bar diameter detection device and detection method for constructional engineering detection, and the device comprises a ring body, a positioning rod is arranged on one side in the ring body, a measuring rod is arranged on the opposite side, the positioning rod and the measuring rod extend inwards, the extension directions are located on the same straight line, and the inward end of the positioning rod is of a linear plane structure. The linear plane structure is perpendicular to the extension line of the positioning rod and the measuring rod and the plane where the ring body is located, and the ring body is provided with a mounting hole which penetrates through the ring body from outside to inside and is used for mounting the measuring rod. According to the technical scheme, the ring body forms a mounting base of the positioning rod and the measuring rod, the distance between the inward ends of the measuring rod and the positioning rod is an initial measurement calibration siz