Abstract: With the development of the construction of shared tower, the problem of electromagnetic interference of base station antenna to transmission line on-line monitoring equipment emerges. Based on the EMC standard of on-line monitoring equipment, the mechanism of electromagnetic interference from base station antenna to on-line monitoring equipment is revealed. By establishing a passive interference solving model for electrically large metal scatterers and using PO-MOM hybrid algorithm to solve the induced current generated by the base station antenna on the surface of the tower, the scattering electric field values at the on-line monitoring equipment are obtained. Taking Shandong Province 35 kV shared tower as an example, the variation of scattering electric field under different working conditions, such as tower head type, antenna power and antenna inclination angle, is analyzed with antenna working frequency and the distance between antenna and on-line monitoring equipment as variables. The results show that the type of tower head has less influence on the interference, while the antenna power and inclination have greater influence on the interference. Based on this calculation, it is suggested that the protection distance between antenna and on-line monitoring equipment should be 18 m.