Abstract: An online voltage control method for coordinating multi-type reactive power resources is provided. First, a linearized power flow equation of branch reactive power is established, and an online voltage control model of multi-type reactive power resources including an objective function and constraint conditions is constructed. The constraint conditions includes generator reactive power constraints, reactive power compensator constraints, transformer tap position constraints, a nodal reactive power balance constraint, and slack contained nodal voltage constraints. Then, an optimization result of voltage control is obtained by solving the model.