The invention discloses a steel shape parameter measuring method and system. The method comprises the steps of utilizing a first sensor and a second sensor on extension cords of two ends of any diameter of a steel to carry out displacement scanning along the length direction of the steel; carrying out smooth filter processing on the displacement data; utilizing an average value to divide the dataafter the smooth filter processing into a plurality of subsets and solving L1-LEN, L1, H1-HEN, H1, L2-LEN, L2, H2-LEN and H2; and utilizing the L1-LEN, L1, H1-HEN, H1, L2-LEN, L2, H2-LEN and to obtainshape parameter data of the steel. The method is free of manual operation, high in measurement speed and high in measurement precision; compared with the traditional manual detection which utilizes vernier calipers, the method is not easy to be interfered by human factors, good in detection process stability and low in requirement for the detectors, is capable of measuring plenty of shape parameters of the steels at the same time, and is capable of obtaining the data such as screw pitches and heights of the surface threads and obtaining the data such as rib widths, rib distances and rib heights of spiral rib steels when the steels are deformed steels.