A series of irradiation experiments were performed using Fusion Neutronics Source (FNS) at JAEA for the investigation of activation of materials relevant to Lithium/vanadium-alloy and Flibe/vanadium-alloy blankets. The specimens of V-4Cr-4Ti, Er and Teflon in 10 mm×10 mm×0.03-0.1 mm were prepared for studying the activation of V-alloy structure, MHD coating of Er2O3, and F in molten salt Flibe, respectively. Be, Li and Li/Be mock-ups were assembled with Be and solid Li blocks in addition to the assembly for direct D-T neutron irradiation to examine the dependence of the activation on neutron spectrum. The neutron spectra in all irradiation locations were calculated using MCNP code and JENDL-3.3 file. The activities of the specimens induced in various neutron fields were measured with a high purity Ge detector (HP-Ge). Experimental analyses were carried out using FISPACT-2001 codes with both EAF-2001 file and FENDL/A-2.0 & FENDL/D-2.0 libraries. The typical calculation/experiment (C/E) values lay in the range of 0.8-1.2. Coarse group treat for (n,) reactions, especially in resonance range, could result in overestimation. Use of continuous cross section improves consistency of the calculation with the experiment. However, accurate estimate of spectra is necessary when the flux changes largely with energy around the threshold or the resonance peak.