The invention provides a small concentrated liquid A supply device and method. The device comprises a liquid inlet pipe, a liquid distributing container, a liquid mixing pipe, a liquid storage container and a liquid supply pipe which are sequentially communicated, and a first liquid sucking pump, a second liquid sucking pump and a third liquid sucking pump which are connected with the liquid mixing pipe. A liquid mixing device is arranged on the liquid distributing container and stirs a sodium chloride raw material and purified water to prepare a sodium chloride solution. The liquid distributing container is connected to the liquid storage container through the first liquid sucking pump and the liquid mixing pipe. The liquid inlet pipe is connected to the liquid mixing pipe through the third liquid sucking pump. The second liquid sucking pump conveys ion liquid to the liquid mixing pipe. The liquid supply pipe of the liquid storage container is connected to a hemodialysis machine. A purified sodium chloride solution is obtained through the liquid mixing device and a dual-layer filter. Through the cooperation with the work of the multiple liquid sucking pumps, concentrated liquid A is obtained in real time, the whole process is fully automatic, and efficiency and convenience are achieved.