As for the multi HVDC transmission lines on the same tower, with a wide application prospect, research on how the fault identification and protection configuration are influenced by the HVDC line layout and fault mode is important to the safe and reliable operation. Devise methods are comprehensively applied in the simulation platform establishment, including the AC grid equivalent, digital electromagnetic transient models establishment, typical line fault’s simulation scheme, and so on. The characteristics of dc line protection such as traveling wave, derivative, dc under-voltage and longitudinal difference ones,in typical faults are studied, influence mechanism and change performance are explored. The results show that the existing dc line protection can effectively identify most typical faults, while it is difficult to identify the specific fault of the specific conductor layout. In the dc lines design, specific conductor layout is suggested to be avoided aiming at improving identification and response ability of dc line protection on fault. Considering the solid theoretical foundation, clear research route, the proposed technical routine will support design, construction, operation and maintenance, is valuable for engineering application.