Disclosed is an electrolyte for a lithium metal secondary battery and a lithium metal secondary battery including the same. An electrolyte system is intended to maintain the energy density of a secondary battery based on a lithium metal negative electrode and to extend the life of a battery. Particularly, an electrolyte for a lithium metal battery which forms a stable SEI film capable of inhibiting formation and extension of lithium dendrite so that the negative electrode of a lithium metal battery having a high possibility of battery ignition may be stabilized and an internal short-circuit may be prevented, and a lithium metal secondary battery including the same is provided.