Traveling wave protection for an HVDC transmission system has a high requirement on sampling frequency and performance is affected by fault resistance and noise interference. Therefore, it is necessary to combine traveling wave protection with pilot protection to identify the fault location. However, the pilot differential protection is susceptible to the influence of distributed capacitance, the amount of data transmitted by the protection device is large, and the action speed needs to be improved. To solve these problems, a pilot protection scheme for the hybrid HVDC transmission system based on an approximate entropy change criterion is proposed. Approximate entropy requires less data to calculate and has the advantages of high sensitivity and reliability. After a fault occurs, obvious peak characteristics emerge in the approximate entropy change. The protection criterion constructed based on the approximate entropy change of 1-mode voltage can recognize the high-resistance ground fault quickly and accurately, and at the same time reduces the influence of noise interference and distributed capacitance. The proposed protection scheme is verified based on a simulation model of the Wudongde ±800 kV hybrid DC transmission system. The results show that the proposed protection scheme requires only a 5 kHz sampling frequency without strict time synchronization. The proposed protection scheme acts correctly and quickly with an 800 Ω grounding resistance fault and under 10 dB signal-to-noise ratio interference.