The invention relates to a fast fault detection method and a fast fault detection system for high-voltage DC equipment. The method comprises the following steps: acquiring the voltage and current signals of a line and the working state information of a power line measurement system through the power line measurement system; acquiring the criterion value of a high-voltage DC equipment protection system; judging whether the measurement system fails; if the measurement system fails, sending the working state information of the measurement system to the high-voltage DC equipment protection system, and making a corresponding response according to the working state information; if the measurement system does not fail, comparing the criterion value with the voltage and current signals to judge whether high-voltage DC equipment fails; and if the high-voltage DC equipment fails, uploading the fault information and physical quantities to the protection system. Through the technical scheme, the fault current can be acquired accurately and the fault current signal can be processed within tens of microseconds in a strong electromagnetic environment with current and voltage changing transiently and at high speed, and the requirement for minimum fault response time is satisfied.