The invention provides a lithium-sulfur battery, in which a sacrificial anode is additionally installed. The sacrificial anode contains at least one of metallic lithium, lithium alloy and a lithium-containing compound. During assembling of the battery, the sacrificial anode is arranged inside or outside a battery core composed of a positive electrode, a diaphragm and a negative electrode. After an electrolyte is injected into the battery and the battery is sealed, there exists voltage difference between the sacrificial anode and at least one electrode of the positive electrode and the negative electrode. By charging or discharging the sacrificial anode with the electrode which has voltage difference with the sacrificial anode, the sacrificial anode undergoes anodic polarization and dissolves out active lithium ions into the electrolyte. The preparation technology of the lithium-sulfur battery is simple. The adopted sacrificial anode can provide active lithium ions for a battery system with lean lithium or no lithium and simultaneously can supplement active lithium ions consumed by an irreversible reaction so as to prolong cycle life of the lithium-sulfur battery.