Based on the analysis of the transmission capability of double-circuit transmission lines on the same tower in fault states and unbalanced states using six-sequence component method， an optimal trip scheme for double-circuit transmission lines on the same tower is proposed. Compared to the traditional trip schemes， the proposed scheme has advantages on maintaining the system transmission capability， and restraining the unbalanced components injected into system. It is available to improve the system stability， and creates better operation conditions for auto-devices like auto-recloser. Dynamic simulation and BPA simulation have proven the conclusions.