Line commutated converter-modular multi-level converter (LCC-MMC) parallel multi-terminal hybrid DC transmission system combines the technical advantages of line commutated converter-high voltage direct current (LCC-HVDC) and modular multi-level converter-HVDC (MMC-HVDC). However,due to its inconsistent boundary characteristics,special busbar structures,and different control strategies for converter stations,the existing line protection schemes are difficult to apply directly. Therefore,a protection scheme of multi-terminal hybrid DC line based on measuring wave impedance phase characteristics is proposed. Firstly,the expressions of wave impedance measured at different fault locations are deduced,and it is found that in the high-frequency band,the phase of wave impedance measured at the measurement point is significantly different under the condition of internal and external faults. And the phase characteristics have nothing to do with factors such as fault distance,type and transition resistance. Then,the S-transform is used to extract the impedance phase information of the measured wave,and combined with the high-low frequency energy ratio criterion of the traveling wave to realise the fault identification. Finally,the simulation verification in PSCAD shows that the proposed protection can distinguish the faults of the T-zone bus and the adjacent line end,and has a certain anti-transition resistance (500 Ω) and noise immunity (20 dB) while satisfying rapidity. The proposed peotection meets the main protection requirements of the multi-terminal hybrid DC system line.