As Wind Energy Conversion Systems, which don't join in grid frequency regulation, take a much more important part in power grid, frequency becomes a big problem. To solve this problem, we present a new method to improve Wind Energy Conversion Systems control strategy using in power grid frequency regulation. At first bases on inertial control it introduces frequency regulation to WECS. Then it improves inertial control with WECS's advantage, capable of changing its output active power arbitrarily within range in a short time, makes WECS contributes more in frequency transient's beginning. Finally it makes WECS cooperates with conventional generators, makes up disadvantage that WECS only can support frequency regulation in a short time, this will make power injection between frequency transient more reasonable, decrease the frequency fluctuation, optimize the WECS output active power curve and achieve rotor speed's recovery. At the end of the paper is simulations results and analysis.