The experimental apparatus for preparing high-concentration calcium chloride solution， production line includes reactor R101,reactor R102, hopper V101, liquid storage tank V102, acid gas absorption tank V104, acidic finished liquid storage tank V105, and a small induced draft fan. It also includes pumps, sensors, valves, pipelines, and supporting equipment, including instrumentation and electrical components. It controlles by a PLC system. The production of high-concentration calcium chloride solution using alkali residue and hydrogen chloride tail gas as raw materials is divided into three stages. In the first stage, the alkali residue and waste calcium solution are mixed in proportion and then hydrogen chloride gas is introduced into the mixture to react, producing a preliminary acidic finished liquid. In the second stage, magnesium ions are removed from the preliminary finished liquid to produce a second alkaline finished liquid. In the third stage, the second-step finished liquid is filtered to obtain a finished liquid. The finished liquid can then be used as raw material to react with the alkali residue for further concentration.