The paper introduces the basic structure and equivalent circuit model of Unified Power Flow Controller (UPFC) in the beginning, and then analyzes its effects on transmission line distance relay in two cases. Different location of the UPFC, the fault resistance, the parameters of UPFC, the location of fault and system operation conditions will all affect the measured apparent impedance to some degree. The presence of UPFC will make the relay under-reach or over-reach. In order to eliminate the effects of UPFC device on protective relay, two methods are given in this paper. One is to equip protective relay devices in which the UPFC device is equipped. In this way the UPFC device is always beyond the fault loop. The other is to use Artificial Neural Network to eliminate the effects of UPFC device.