In a method for establishing a safety plane in coordinate measurements, the method meshes a 3D model of a workpiece and a probe by triangles, and calculates a maximum bounding box of the probe. The method further obtains a moving path of the maximum bounding box after moving the maximum bounding box from a first measuring point to a second, and obtains a maximum space box of the moving path. If the maximum space box has one or more intersections with the workpiece, the method calculates a distance between vertices of each of the triangles falling within the maximum space box and a bottom face of the maximum space box, and obtains a point in the bottom face of the maximum space box that has a maximum distance from the triangles. By correcting a plane containing the point, the safety plane is obtained.