In order to improve receiving-end frequency stability of AC power grid with MMC based HVDC (MMC-HVDC), a frequency stability enhancement control strategy based on frequency limit controller (FLC) and modified virtual synchronous generator (VSG) is proposed in this paper. When power disturbance occurs in the receiving-end grid, the receiving-end MMC adopting the proposed control strategy can provide emergency power support for the disturbed power grid, which can not only improve system damping and frequency oscillation, but also realize the steady-state transmission power of DC system controllable. The effectiveness of the proposed control strategy is verified by theoretical analysis and simulation in PSCAD/EMTDC.