The invention relates to a full-automatic single-cylinder mold lifting device of an egg tray machine. The full-automatic single-cylinder mold lifting device of the egg tray machine comprises an upper mold, a lower mold and a cylinder and is characterized in that the single cylinder is adopted for transmission, and guide devices are further arranged between the upper mold and the lower mold; each guide device comprises a base, a protecting sleeve, a bearing bush and a guide post; the bases are fixedly mounted on the lower mold, and the guide posts are fixedly mounted on the bases; the protecting sleeves are fixed to the upper mold, and the bearing bushes are embedded in the protecting sleeves; the guide posts are sleeved with the bearing bushes and guide the upper mold to slide up and down. According to the full-automatic single-cylinder mold lifting device of the egg tray machine, traditional double cylinders are replaced by the single-cylinder structure, and thus mechanical losses caused by asynchronization are avoided effectively; the guide devices are arranged additionally, and therefore the upper mold can only move in the direction of the guide posts in the vertical movement process, it is ensured that the molds cannot deviate, and the upper mold and the lower mold are combined very tightly. Compared with exiting egg tray machine devices, the service life of the device is greatly prolonged, and operating cost is reduced. The full-automatic single-cylinder mold lifting device of the egg tray machine is simple in structure, low in cost and suitable for being used and popularized on a large scale.