The Great East Japan Earthquake (March 11, 2011) has inflicted enormous damage on the accelerator facility of Research Center for Electron Photon Science, Tohoku University. A 300 MeV linac operated for 46 years as an accelerator for radioisotope (RI) production and also as an injector of a 1.2 GeV booster synchrotron for nuclear physics experiments. The low energy part of the linac will be rebuilt with all the recyclable components and will be run for RI production. New small linac is constructed as the injector for the booster synchrotron. The injector consists of a thermionic rf-gun, an alpha magnet, two 3mlong accelerating structures, and transport line to the synchrotron. The maximum energy of injector is 90 MeV with beam loading. The detail of the injector linac is introduced in this conference.