In a medical linear accelerator, the primary and secondary collimators are generally made of high atomic weight metals. The energy of the x-rays generated by accelerated electrons exceeds the bonding energies of high atomic number materials such as tungsten, and lead in the structure of the components in the accelerator head, it causes the production of neutron from the nucleus. Consequently, the resulting photo-neutrons can easily be scattered and spread into the treatment room. Thus, an additional neutron dose cannot be ignored in the tumor volume of the patient and in areas outside this volume. The contribution of the primary and secondary collimators to the neutron contamination is found to be approximately 52% and 30%, respectively. In this paper, the effects of using different composite materials such as Boron, Cadmium, and Polyethylene in secondary collimators on neutron contamination have been investigated by using Fluka Monte Carlo and TALYS 1.9 codes.