Abstract: A different on-line beam radius diagnosis structure based on the principle of diamagnetic loops was proposed. This structure can distinguish beam information from magnetic field at the same time, from which we can obtain beams' radius and currents. This paper focuses on the probe structure, equivalent circuit and experiment simulation platform. It analyzes the homogeneity of electric field information and puts forward the improvement measures, then compares the measurement results before and after improvement to illustrate the effectiveness of the structure. It shows that the consistency of the electric field signals increases from 94.08% to 99.60%. The simulated screwrods' radius errors are within 1 mm.