A steam pasteurization method for freeze-dried food comprises: 1) determining a corresponding pasteurization temperature according to a type of a freeze-dried food item requiring pasteurization, and a target water activity at the pasteurization temperature； 2) cooling and lowering the temperature of the food item in step 1) to a cooling temperature corresponding to the food type； 3) removing air in a pasteurization chamber accommodating the food item by means of a vacuum pump； 4) charging steam into the pasteurization chamber, after the temperature of the food item reaches the pasteurization temperature, regulating a flow of the steam to keep the food item temperature at the pasteurization temperature for a specific duration, and then terminating the charging of the steam； 5) capturing the steam and lowering the pressure in the pasteurization chamber； and 6) after the pressure in the pasteurization chamber reaches or approximates a water saturation pressure corresponding to the cooling temperature before pasteurization, charging clean air into the pasteurization chamber until the chamber is not in a vacuum state, and discharging the food item to complete the process.
