In this paper, firstly the spectral response of transmission-type GaAs photocathode is measured online by the spectral response-testing instrument. Then the cathode is sealed in the third generation intensifier and put into the instrument again to get another spectral response curve. The variation of spectral response curves was compared. The results show that through the seal process, the spectral response in the long wavelength decrease. Based on these curves, the spectral matching factors of GaAs photocathode for green vegetation and rough concrete are calculated. The calculated performance parameters show that the variation of the spectral response in the seal process is an important influence factor on the performance of the intensifier in the use of night vision. (c) 2005 Elsevier B.V. All rights reserved.