Abstract: The CLIC project is based on the two beams concept that one beam (drive beam) is decelerated to produce the required RF power to accelerate another beam (main beam). The drive beam is produced and accelerated up to 50MeV inside the CLIC drive beam injector. The main components are a thermionic electron gun, three or four sub harmonic bunchers, a pre-buncher, a TW buncher, 13 accelerating structures and one magnetic chicane. IPMs contribution was the longitudinal and beam dynamics study and the thermionic gun, photo-cathode RF gun, pre-buncher, sub harmonic bunchers and traveling wave buncher design. In this presentation these contributions will be reviewed.