The invention discloses a longitudinal connecting protection method for identifying inner and outer faults of a hybrid double-end DC power transmission line area. The method comprises the steps of ina converter station, acquiring a current magnitude signal from a current sensor at a local-pole DC power transmission line side; calculating a current fault component according to the local-pole current; calculating summation of the current fault components in a selected fault data window length, and when the summation is higher than a starting threshold value, performing starting protection; whenthe current fault component is same with a reference direction, determining the phase to 0 DEG; and when the current fault component is opposite from the reference direction, determining the phase to-180 DEG C. When the fault occurs in the DC line, the phases of the current fault components of the converter stations at two sides are same. When the fault occurs outside an area, the phases of thecurrent fault components of the converter stations at two sides are opposite. According to a fact that the phases of the current fault components at a rectification side and an inversion side are same, determining for the in-area fault and the outer-area fault of the hybrid double-end DC power transmission line area can be performed. The method according to the invention has advantages of low requirement for sampling frequency of the protecting device, easy realization, high reliability and high transition resistance.