NOVELTY - Chemical bath deposition system (10) for forming a buffer layer on at least one back electrode substrate (1) having a photoelectric transducing layer (3), comprises: a chemical bath tank (12) for storing a buffer layer solution comprising a cation and an anion; a chemical-solution purification device (14) communicated with the chemical bath tank for removing residual cation to obtain a purified solution after the cation reacts with the anion to form the buffer layer; and a dosing device for performing compensation of the cation according to a component ratio of the purified solution.    USE - The chemical bath deposition system is useful for forming a buffer layer on at least one back electrode substrate having a photoelectric transducing layer (claimed).    ADVANTAGE - The chemical bath deposition system: utilizes the analyzing method or the theoretical calculation method, and thus allows obtaining the component ratio of the purified solution more precisely since the buffer-layer forming reaction in the purified solution has been stopped; directly utilize the recycled buffer-layer solution to perform the buffer-layer forming process on subsequent back electrode substrates, since the dosing device reduces the reacted buffer-layer solution back to its original state in a component dosing manner; and directly utilize the purified cleaning solution to clean subsequent back electrode substrates, thus decreasing the solution cost of the solar battery manufacturing process in cleaning the back electrode substrate, and improving the quality of the formed buffer layer.    DETAILED DESCRIPTION - Chemical bath deposition system (10) for forming a buffer layer on at least one back electrode substrate (1) having a photoelectric transducing layer (3), comprises: a chemical bath tank (12) for storing a buffer layer solution comprising a cation and an anion, where the cation is used for reacting with the anion to form the buffer layer on the photoelectric transducing layer when the back electrode substrate is placed in the chemical bath tank to be immersed in the buffer layer solution; a chemical-solution purification device (14) communicated with the chemical bath tank for removing residual cation to obtain a purified solution after the cation reacts with the anion to form the buffer layer; and a dosing device for performing compensation of the cation according to a component ratio of the purified solution.    DESCRIPTION OF DRAWING(S) - The figure shows a functional block diagram of the chemical bath deposition system.    Back electrode substrate (1)    Photoelectric transducing layer (3)    Chemical bath deposition system (10)    Chemical bath tank (12)    Chemical-solution purification device (14)