The invention provides a distribution network voltage control method and system based on synchronous measurement and sensitivity estimation. The method is characterized by comprising the following steps: obtaining positions and numbers of voltage observation nodes and reactive power regulation nodes equipped with synchronous measurement devices based on the topological connection relationship of the distribution network; determining the voltage control priority of each reactive power regulation node relative to each voltage observation node based on the positions of the voltage observation nodes and the reactive power regulation nodes; and performing reactive power regulation based on the current voltage measurement value of the voltage observation nodes and the voltage control priority ofeach reactive power regulation node relative to each voltage observation node. The historical information of voltage control is obtained by using synchronicity of the voltage and power measurement ofthe synchronous measurement devices, and the established voltage reactive power sensitivity model parameters are estimated through the historical information so that the goal of voltage control is realized by only relying on the measurement information of part of the nodes.