Abstract: In the construction of smart grid infrastructure, the quality of reinforced concrete is related to the safety of smart substations, transmission lines and other projects. One of the conditions for the stability of reinforced concrete structures is whether the diameter of the steel bars used meets the standard. In order to achieve nondestructive testing of the diameter of concrete steel bars, a concrete steel bar diameter eddy current testing method based on the random forest support vector machine stacking ensemble algorithm was proposed. Firstly, the principle of eddy current testing for steel bar diameter in concrete was analyzed using eddy current testing technology; Secondly, a finite element model for eddy current detection of steel bar diameter was established, and the experimental process of dynamic eddy current detection of steel bar diameter was designed to obtain eddy current detection signals and perform preprocessing; Finally, a stacking ensemble algorithm based on random forest support vector machine was used to construct a prediction algorithm for concrete steel bar diameter. Simulation verification was conducted on reinforced concrete specimens of different specifications, and the experimental results showed the effectiveness and accuracy of this method.