A new stochastic unfolding algorithm (SUA) based on the iterative process was developed for the adjustment of the priori spectrum. Genetic algorithm (GA) has also been applied for unfolding and adjusting the neutron energy spectrum by foil activation method to minimize the difference between measured and modified priori spectrum. The cross sections used were from the JENDL3.3 libraries. The adjusted fluxes were verified by calculating the activities for 58 Ni(n,p) 58 Co and 58 Co(n,γ) 59 Co and comparing the results with measured values. The results obtained from SUA gives final DEV in the activities, of 22.505% and the relative errors for 58 Ni(n,p) 58 Co and 58 Co(n,γ) 59 Co, of 10.01% and 4.17% respectively. The priori flux spectrum was adjusted successfully with a DEV of 17.6563%. The relative errors for 58 Ni(n,p) 58 Co and 58 Co(n,γ) 59 Co became 34.37% and 0.16% respectively.