The invention provides a control method for a battery energy storage system participating in primary frequency modulation of a power grid, which adopts three frequency modulation modes, namely, virtual inertia response, virtual negative inertia response and virtual droop control, to participate in frequency modulation of the power grid according to different working conditions of the power grid. When the frequency is in a deteriorated working condition, virtual inertia response and virtual droop control are adopted to jointly participate in frequency modulation of the power grid; and when thefrequency is in the recovery working condition, virtual negative inertia response and virtual droop control are adopted to jointly participate in frequency modulation of the power grid. According to the frequency modulation control strategy, frequency deviation and frequency deviation change rate characteristics in the primary frequency modulation process are comprehensively considered, the advantages of the virtual inertia mode and the virtual droop mode are combined, comprehensive use of the three control modes at the same moment is achieved, the primary frequency modulation effect is improved, and the energy storage capacity requirement is reduced.