Abstract: The key of image fusion technique is to select appropriate fusion arithmetic and fusion rule in order to analyze the impact of fusion rule to the fusion performance，four fusion rules are adopted to perform fusion experimentation with AVHRR and MODIS images and six statistical indexes are used to compare the fusion capability.This paper draws the conclusions that there are some capability differences between different rules and the fusion capability is different in different index even using the same rule.It is preferable to select fusion rules according to image fusion aim.