A three-dimensional (3D) collision detection method for a measuring machine comprises the steps of: receiving parameters of a to-be-measured workpiece and a moveable arm; simulating a to-be-measured workpiece 3D-model in accordance with the parameters of the to-be-measured workpiece, and a moveable arm 3D-model in accordance with the parameters of the moveable arm; combining the to-be-measured workpiece 3D-model with the moveable arm 3D-model to form a 3D collision model; generating a measuring path of the moveable arm by calculating positional coordinates of the moveable arm according to the 3D collision model; detecting whether the moveable arm collides with the to-be-measured workpiece according to the measuring path; and outputting collision results that include the collision coordinates and the measuring path. A related system is also disclosed.