The mainstream protection scheme of DC power grid is using DC breakers to remove faults at present. However, HVDC breaker is expensive and it is costly for each DC line equipped with DC breakers. Firstly, a partition protection strategy suitable for future large-scale DC grid is proposed, which aims to minimize the number of DC breakers and ensure the reliability of power supply. Secondly, the influence of partial power interruption which caused by fault DC area on the system is qualitatively analyzed. Then the basic partition principle of DC grid is formulated, considering unbalanced power, the mode of system-level control and the type of converters. Besides, according to the characteristics of DC breakers, AC/DC converters, DC/DC converters, AC breakers, high speed switches and other fault removal components, the timing coordination strategy is formulated in detail. Finally, a seven-terminal DC power grid is modeled in PSCAD/EMTDC simulation platform. The simulation results verify the correctness of the proposed partition protection strategy and the corresponding timing coordination strategy of DC grid.