The utility model relates to an automatic gas sample injector, which comprises a base, a sample injecting device, a positioning device, a bottle stopping arm, an action mechanism, a supporting device, a control device and a power supply. The sample injecting device comprises a two-way electromagnetic valve, a straight joint, a syringe needle seat, a syringe head and a plurality of sample containers; and the injection head and the sample containers are installed on the syringe needle seat. The positioning device comprises a side shaft capable of rotating and lifting; the side shaft is arranged on the base; an upper air cylinder support, a lower air cylinder support and a bottle baffling arm are transversely arranged on the side shaft; and two air cylinder fixed seats are respectively arranged on the upper air cylinder support and the lower air cylinder support. The action mechanism comprises a compressed air source, a needle inserting electromagnetic valve, a needle withdrawing electromagnetic valve and double-way air cylinders; the needle inserting electromagnetic valve and the needle withdrawing electromagnetic valve are arranged on the base; and the double-way air cylinders are arranged on the air cylinder fixed seat. The supporting device comprises a main shaft, a guide disc, a guide arm and a sample disc; the main shaft is arranged in the center of the base; the guide disc and the sample disc are sleeved on the base; a screw type guide groove is arranged on the top surface of the guide disc; and cogs are arranged on the periphery of the guide disc. The control device is used for controlling action of the sample injecting device and the action mechanism. The automatic gas sample injector is adapted to the field of environmental protection, capable of meeting automatic sample injecting requirements when gas samples for detecting air quality are analyzed.