The invention discloses an electrochemical preparation method of an electrodeposited silver iodide semiconductor film, which comprises the following steps: 1. flushing ITO conductive glass or a silicon slice for 2 to 3 times through acetone, then cleaning the ITO conductive glass or the silicon slice placed in an ultrasonic cleaner through deionized water, next placing the ITO conductive glass orthe silicon slice into 10% nitric acid solution for activation, and finally repeatedly flushing through the deionized water; 2. mixing 0.002 to 2mol/L of AgNO3, 0.002 to 2mol/L of KI and 0.002 to 2mol/L of ethylene diamine tetraacetic acid disodium salt, and regulating a pH value to 7 to 13 through 2mol/L of HNO3 or 0.1mol/L of NaOH solution to obtain an electrolyte; and 3. carrying out electrodeposition by using the ITO conductive glass or the silicon slice as a working electrode, using a platinum sheet electrode as a counter electrode and using a saturated calomel electrode as a reference electrode to obtain the silver iodide semiconductor film, wherein the electrodeposition voltage of the relatively saturated calomel electrode is 1.1 to 2.5V, and the electrodeposition temperature is 25to 80 DEG C. In the invention, silver iodide with certain orientation and crystalline form is synthesized in one step through electrodeposition, and the invention has simple equipment, low cost and lower requirements for reaction conditions.