Abstract: Since the curve shape of activation cross-section with neutron energy is different for target nuclide of activation foil and single-crystal silicon, the determined value of equivalent 2 200 m/s thermal neutron fluence rate from activation foil method may have some deviation with the value corresponding with the target activation rate of single-crystal silicon. In order to investigate the influence of different variations of activation cross-section on measurement, the measurements on the Zr and CoAl foils were compared. The thermal neutron cross-section of Zr and CoAl foils separately obeys the 1/v law, but the ratio between resonance integral and 2 200 m/s thermal neutron activation cross-section is much different from each other. The result shows that the determined value by Zr foil is much larger than that by CoAl foil because of the greater contribution from epithermal neutron to activation rate of the former, and the difference of activation cross-section variation has significant influence on the measurement result. In order to eliminate the influence, the method of simultaneous equations built by the relational expression of Stoughton-Halperin convention and the determined values from two kinds of foils was used. As a result, the equivalent 2200 m/s thermal neutron fluence rate corresponding to target activation rate of single-crystal silicon was determined.