The invention provides an active support power grid frequency response control method and system. The method includes the following steps: obtaining the frequency deviation of a power grid based on acollected power grid frequency; comparing the frequency deviation of the power grid with a preset frequency deviation limit to determine the response mode of an energy storage system; and determiningthe operation power adjustment value of the energy storage system according to the response mode. According to the technical scheme of the invention, different working modes are set for the energy storage system so that the energy storage system can reasonably arrange the output size and depth according to the frequency fluctuation degree of the power grid and its own SOC condition, which not onlyembodies the initiative of the energy storage system, but also has the friendliness to the power grid connection. The sag gain is determined for active support by simulating the sag characteristics of a traditional generator set and considering the constraints of the energy storage system itself, which reflects the accuracy of system response.