A method of calibrating a 3D (three dimensional) camera, comprising: pre-calibrating a 2D (two dimensional) camera coordinate system, and arranging the 3D camera to be calibrated in a proximity to a 2D camera; arranging in a common field of view of the 3D camera and the 2D camera a 3D object and a background having color contrast on surfaces between each other; controlling the 2D camera to capture an image, and controlling the 3D camera to capture a point cloud; separating a point cloud of the 3D object and a point cloud of the background captured by the 3D camera, and recording raw colors of the point cloud of the 3D object and raw colors of the point cloud of the background; transforming the point cloud of the 3D object and the point cloud of the background into coordinates in the 2D camera coordinate system using a default value of a predetermined transform parameter; obtaining a transformed color of each point in the point clouds at a position of the 3D object or the background in the image captured by of the 2D camera according to each point of the transformed point cloud of the 3D object, or from positions of the background in the image captured by the 2D camera according to each point of the transformed point cloud of the background; comparing the raw color and the transformed color of each point in the point cloud of the 3D object and in the point cloud of the background to compute a missing score of the point cloud of the 3D object and the point cloud of the background; and determining whether the missing score is less than a predetermined threshold, and if so, determining that a transform mapping from a coordinate system of the 3D camera to the 2D camera coordinate system is completed. pre-calibrating a 2D (two dimensional) camera coordinate system, and arranging the 3D camera to be calibrated in a proximity to a 2D camera; arranging in a common field of view of the 3D camera and the 2D camera a 3D object and a background having color contrast on surfaces between each other; controlling the 2D camera to capture an image, and controlling the 3D camera to capture a point cloud; separating a point cloud of the 3D object and a point cloud of the background captured by the 3D camera, and recording raw colors of the point cloud of the 3D object and raw colors of the point cloud of the background; transforming the point cloud of the 3D object and the point cloud of the background into coordinates in the 2D camera coordinate system using a default value of a predetermined transform parameter; obtaining a transformed color of each point in the point clouds at a position of the 3D object or the background in the image captured by of the 2D camera according to each point of the transformed point cloud of the 3D object, or from positions of the background in the image captured by the 2D camera according to each point of the transformed point cloud of the background; comparing the raw color and the transformed color of each point in the point cloud of the 3D object and in the point cloud of the background to compute a missing score of the point cloud of the 3D object and the point cloud of the background; and determining whether the missing score is less than a predetermined threshold, and if so, determining that a transform mapping from a coordinate system of the 3D camera to the 2D camera coordinate system is completed.