Abstract: In order to verify the feasibility of sensing coating in crack detection of reinforced concrete beam by electrical resistance tomography (ERT) and improve the ERT detection accuracy of cracks, firstly, the correlation between mechanical properties and electrical properties of sensing coating was obtained through experiments. Then, the sensing coating was used to collect the potential difference data of reinforced concrete beam during three-point bending test. Finally, the differential ERT algorithm was used to detect the cracks of concrete beam. The test results showed that the mechanical toughness of the sensing coating and its connection with concrete were good. When the strain was less than 0.35%, it was linearly related to the conductivity. The sensing coating at the crack did not appear to be detached, and the reliability of the original data of ERT detection was greatly improved. The reconstructed image of the difference algorithm can provide qualitative information of concrete cracks, and can visually detect the location and distribution of cracks. Compared with the traditional direct ERT method, the method of detecting concrete defects was more accurate and practical.