Based on the analysis of fault feature of teed circuit of parallel transmission lines， a new fault line selecting method is proposed. When fault occurs， the positive sequence fault components at the bus where the protection relay is installed are used to calculate the mutation voltage and mutation current in order to obtain the related voltages at T node. The ratio of the related differential voltage can be used to identify the faulted line. This method can be used to specify the cross-phase fault and single line fault of the parallel line as well as cross-pole fault. The faulted line can be identified correctly by using the new method. The result of EMTP simulation indicates that this method is not affected by fault resistance and system operating mode. It can also be applied in asymmetrical parallel transmission lines.