The invention discloses a positioning measurement method in an anchor test in a marine rock and belongs to the technical field of civil engineering. For the disadvantages that an error is large and test requirements are not satisfied by a displacement sensor in an existing method of positioning by running a wire, the invention provides the method, the displacement of an anchor is not directly measured, the anchor is magnetized to generate a magnetic field, an optical fiber adheres to a magnetostrictive material, the magnetostrictive material is fixed, in the process that the anchor moves, themagnetic field strength at the magnetostrictive material is estimated by measuring the strain of the optical fiber that is the strain of the magnetostrictive material, then a distance between the magnetostrictive material and the anchor is calculated by a magnetic field intensity formula, and thus the anchor is positioned. Compared with the existing measurement technology, the method of the invention has the advantages that the sensor cannot measure in soil and a measurement error exists when a wireless sensor is installed on the anchor. An anchor trajectory in a marine rock test can be accurately measured.