The invention discloses an automated testing system for a gas cylinder. The system comprises a water return tank, a measuring water tank, a circulating water tank, a measured gas cylinder, a water pressure testing loop used for regulating the pipeline water pressure, a gas pressure testing loop used for regulating the pipeline gas pressure, a four-way joint and a controller; the measured gas cylinder is installed in the water return tank through a support, the cylinder body part is immersed into the water return tank, an opening of the measured gas cylinder faces upwards, and a circulating water pump is arranged between the water return tank and the circulating water tank; the four-way joint is connected with the gas pressure testing loop, the water pressure testing loop, a pressure relieving pipeline and a high-pressure filter separately. According to the automated testing system, the comprehensive capability is high, automation of gastightness testing, strength testing, burst testing and residual deformation measuring of a pressure vessel can be achieved, and experimental results are more precise; the automation degree is high, volumetric measuring of the vessel and pressure increasing, pressure maintaining, pressure supplementing, pressure relieving and the like of the system all can be automatically completed, manual operation is not needed, and safety and reliability are achieved.