The knowledge of (n, 2n) cross section is very important and necessary in the reactor technology since a significant portion of the fission neutron spectrum lies above the threshold of (n, 2n) reaction for the most of the reactor materials. The (n, 2n) cross section is neutron multiplier reaction in fusion reactor design. Therefore, (n, 2n) reactions of the selected blanket materials can play a key role for multiplying neutrons in reactor environment. In this study, for some structural fusion materials (n, 2n) reactions such as (27)Al(n, 2n)(26)Al, (51)V(n, 2n)(50)V, (52)Cr(n, 2n)(51)Cr, (55)Mn(n, 2n)(54)Mn, (56)Fe(n, 2n)(55)Fe and (58)Ni (n, 2n)(57)Ni have been carried out up to 40 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. Also in the present work, the (n, 2n) reaction cross-sections have calculated by using evaluated empirical formulas developed by Tel et al. at 14-15 MeV energy. The calculated results are discussed and compared with the experimental data taken from EXFOR database.