Lithium-air batteries, based on the reaction of lithium with oxygen from air, have very high theoretical specific capacity of 3828 mAh/g and have important potential applications for electric vehicles. This paper reviews the new progress of studies of lithium-air batteries. The structure and operation mechanism of the aprotic system, hybrid aprotic-aqueous system, and solid state system are analyzed. The air electrode, catalyst, and electrolyte of the aprotic system are discussed in detail. The pore volume of the porous carbon is an important structural parameter for the specific capacity of the air electrode. The porous carbon with a large pore volume would possess a high specific capacity because it can provide a large space for lithium oxides formed during the dicharge process. The specific surface area and the average pore size of the porous carbon also affect the specific capacity. Appropriate catalysts can effectively reduce the overpotentials for the oxygen reduction reaction and the oxygen evolution reaction, and consequently, increase the energy efficiency of the battery. The electrolyte with high polarity, low viscosity, low moisture adsorption, and high oxygen solubility is preferable for the performance of the battery. The separator and the electrolyte of the hybrid aprotic-aqueous system are also discussed. The lithium super-ionic conductor glass film with good stability in both aprotic and aqueous electrolyte is very important for the hybrid aprotic-aqueous system. The recent development of the solid state system is commented, including the development direction of this field.