Disclosed is a detection tool for space position of an embedded pipe of a finished board of a CRTS (China railway track system) III type track slab. A spherical-prism seat used for fixing a spherical prism is installed at the top of a cylinder seat, a prism installation groove is arranged in the center of the sphere-prism seat, a seal ring used for positioning the top of the cylinder seat is sleeved outside the sphere-prism seat, the bottom of the seal ring extends to the lateral wall of the cylinder seat, a base placed on a rail cant is fixed at the bottom of the cylinder seat, a tapered rod through hole of the diameter smaller than the inner diameter of an outer casing is arranged in the center of the base, a tapered rod is installed in the cylinder seat, the upper portion of the tapered rod is cylindrical, the lower portion of the tapered rod is in inverted-cone-frustum shape, the cylindrical part of the tapered rod slides vertically along the inner wall of the outer casing, the inverted-cone-frustum part of the taped rod extends downwards to penetrate through the tapered rod through hole in the center of the base to annularly contact with the inner wall of the embedded pipe tightly. The detection tool is simple in structure, convenient in installation, and capable of converting deviation of space position of embedded pipe of the finished board of the track slab to deviation of center of the prism, improving detection efficiency and being widely applied to the detection field of the embedded pipe of the finished board of the track slab in a railway line for passenger traffic.