Several samples of quartz optical fiber coated with UV-cured epoxy acrylates were analyzed with XPS. The results suggested that the nature of functional group of coating mentioned plays an important part in the change of transmitting property for optical fiber. There exists an obvious influence of -C=O or -O-C=O group on the loss of optical fiber: the more the -C=O or -O-C=O group contained in coating, the greater the loss. On the other hand,the increase of the content of -C-C- group could lead to fewer loss.