The invention provides a pressure vessel used for electrolyte injection of a lithium battery. The pressure vessel comprises an upper shell and a lower shell detachably combined with the upper shell. An airtight cavity is formed when the upper shell is combined with the lower shell. A battery positioning support is arranged in a lower cavity body. A plurality of battery positioning grooves with openings facing upwards are formed in the battery positioning support. A connecting surface is arranged on the peripheral edge of the upper end of the lower shell. A connecting ring corresponding to the connecting surface is arranged at the lower end of the upper shell. A plurality of connecting posts which are annularly distributed and extend upwards are arranged on the connecting surface. A plurality of connecting holes corresponding to the connecting posts are formed in the connecting ring. When the upper shell is combined with the lower shell, the connecting posts penetrate through the connecting holes to stretch out of the upper surface of the connecting ring, and clamping parts arranged on the connecting ring are clamped to limiting parts on the connecting posts. According to the pressure vessel used for electrolyte injection of the lithium battery, the battery can be pressurized on the whole during electrolyte injection, the difference between the inner pressure and the outer pressure of the battery is eliminated, and the battery is prevented from being damaged while the electrolyte injection efficiency is improved; and meanwhile, the upper shell and the lower shell are of a detachable structure so that production can be conducted conveniently through automatic equipment.