The embodiment of the invention provides a coordinated control method and system for medium and low voltage distribution networks containing a photovoltaic power supply. The coordinated control methodcomprises the steps that the low voltage distribution network performs local control on reactive power outputted by the photovoltaic power supply based on a voltage-reactive power droop control method; if the voltage does not exceed the limit after the local control, the control is over; if the voltage exceeds the limit after the local control, the locally consumed low voltage distribution network is equivalent to a load node in the medium voltage distribution network with the power being known, optimal power flow (OPF) centralized optimization is performed on the voltage and power of an equivalent load through the medium voltage distribution network, the optimization result is re-checked in the low voltage distribution network, and the above steps are repeated until there is no limit exceeding voltage in the low voltage distribution network. The centralized optimization control model of the medium voltage distribution network is built through equivalence of the low voltage distribution network, and the proposed model is transformed into a second-order cone programming model which can be effectively solved through a second-order cone relaxation technology. Through the coordinate control of the medium and low voltage distribution networks, the local and remote photovoltaic consumption is promoted, and various operation indexes of the distribution network are improved.