The invention belongs to the field of medical equipment and particularly discloses an automatic preparing instrument for glucose water. The automatic preparing instrument comprises a controller, a preparing cabinet and a water storage bucket communicating with the preparing cabinet, wherein the water storage bucket is located above the preparing cabinet, a first storage tank which is used for storing water, a second storage tank which is used for storing glucose and a mixing chamber which is used for mixing the glucose with the water are arranged in the preparing cabinet, a first electromagnetic valve is arranged in the first storage tank and is electrically connected with the controller, an automatic discharging mechanism is arranged in the second storage tank and is electrically connected with the controller, a water outlet pipe communicating with the mixing chamber is arranged on the preparing cabinet, and a water outlet valve is arranged on the water outlet pipe. Compared with manual preparing, the automatic preparing instrument has the advantages that the whole glucose preparing process is completed through mechanical automation, so that the automatic preparing instrument is more timesaving and laborsaving, operations for doctors and nurses are effectively reduced, and the use is convenient.