The invention discloses an automatic weighing device for the water purification amount of a drinking water purification machine. The automatic weighing device comprises the parts of a water purification machine sample, a high-precision electronic scale I, a high-precision electronic scale II, a container barrel I, a container barrel II, an electronic control three-way valve, a water distribution system, a water reservoir, a circulating water pump, a PLC and the like. According to the automatic weighing device, a water container does not need to be replaced manually, thus the labor intensity isreduced, detection automation is achieved, and the detecting quality and efficiency are improved; and in addition, through a weighing method, the cumulative sum of multiple weighing serves as the total water purification amount, the water purification weight difference between the container barrels each time is extremely small, thus the total cumulative error is also small, the testing result ismore accurate, the detecting quality is improved, and the detecting dispute is avoided.