Abstract: The multiple group cross sections are indispensable when we want to obtain the neutron spectrum by multiple foil activation method. In the paper, the multiple group cross sections and processing technique based on original evaluated database were developed. For different thickness activation foils, especially nuclear reactions with large absorption or scattering cross section, it’s better to process new group cross sections based on the infinite dilution group cross section for different thickness foils. To different thickness foils wrapped by cadmium, it’s better to use MCNP code to calculate their group cross sections, the neutron absorption and scattering by cadmium and foil itself can be considered by this code. It cannot be adapted directly the groups cross sections in the literature (or used by others). In the experimental data processing, the analysis was carried on to all kinds of foils which were massively used at present. The accuracy of multiple group cross sections was verified by experiments.