A method for calibrating a depth of a 3D camera includes selecting a calibration plane and obtaining a first depth image of the calibration plane using a 3D camera when a distance between the 3D camera and a calibration plane is a standard distance. A first depth image, represented by a first phase values of pixel points, is obtained. Then obtaining a second depth image of the calibration plane using the 3D camera when a distance is a testing distance, and intercepting the phase values of the pixel points of the two-dimensional image region and deleting the phase values of the pixel points of the non two-dimensional image region in the second depth image. Calculating and outputting predicted phase values of pixel points in the non two-dimensional image region of the second depth image and calibrating the second depth image.