The utility model discloses a bleaching liquid preparation device for mine sewage treatment, which comprises two stirring tanks, a water supply pipe is arranged right above each of the two stirring tanks, and a storage tank is arranged on one side above each stirring tank; a first motor is arranged outside the middle of the stirring tank, an output shaft of the first motor is fixedly connected with a horizontal rotating shaft, and stirring blades are arranged in the stirring tank of the horizontal rotating shaft; a second motor is arranged below the stirring tank, an output shaft of the secondmotor is fixedly connected with a vertical rotating shaft, a pair of horizontal stirring rods is arranged at the position, located in the stirring tank, of the vertical rotating shaft, and output pipelines with one ends communicating with the interior of the stirring tank are arranged at the bottom of the stirring tank. When in use, the two stirring tanks are respectively used as a batching tankand a buffer tank, and when one stirring tank supplies bleaching liquid into a mine, the other stirring tank can perform size mixing reaction, so that the two stirring tanks are alternately used, andnormal production is guaranteed.