The invention discloses a wall thickness and wall thickness difference measurement tool of a bipyramid any cross section. The measurement tool comprises a base, a support plate is arranged at a left end of the base, a first circular conical surface is arranged at a right side of the support plate, three bearings I are uniformly distributed on a normal of the first circular conical surface, three bearing bushes I on three bearings I form a second circular conical surface; a rear support is arranged at the right end of the base, a thimble shaft is arranged on the rear support, and a third circular conical surface is arranged on the thimble shaft; a sliding plate is arranged on the base and capable of sliding along a guide rail slot on the base; a table skeleton rod is arranged on the slidingplate, a dial indicator is arranged on the table skeleton rod, and a measuring bar is fixedly arranged on the sliding plate. By ingeniously utilizing the guide rail slot structure, a bearing rotary structure is used for reflecting the change of the wall thickness and the wall thickness difference of any cross section in the measured length range to the dial indicator; and the problem that the wall thickness micrometer and like conventional measurement tool cannot measure the wall thickness and wall thickness difference of composite cone, deep and hole parts is solved.