Abstract: A disposable safety syringe with an automatically retractable needle is provided, which comprises a cylinder, a plunger and a needle seat. The needle seat is comprised of a large needle seat and a small needle seat, in which the large needle seat is connected with the cylinder. The small needle seat is disposed within the large needle seat for mounting the needle. The interior of the plunger is a through hole and an elastically reset device is provided in the front portion of the through hole for taking the small needle seat back into the through hole of the plunger after injection. The safety syringe according to the present invention is reasonable and simple in structure, easy in processing, low in cost and is superior and reliable in performance.