The invention discloses a start-stop method of a multi-terminal flexible direct current power transmission system. The system comprises a multi-terminal voltage source type converter connected via a direct current line, a direct current side of the voltage source type converter comprises a pole isolation device (an isolation switch or a direct current breaker), and an alternating current side comprises a wire-inlet switch, a charging resistor, and a charging resistor bypass switch or a switch connected with the charging resistor in parallel. In the start-stop method, the start process includes following steps: direct current line pole connection of a to-be-operated converter; charging of the to-be-operated converter; unlocking of the converter of a constant direct current voltage control station and establishment of direct current voltage; and unlocking of the converter of a non-constant direct current voltage control station. The stop process includes following steps: reducing the active power and reactive power of the converter of the non-constant direct current voltage control station to certain values; locking the converter of the non-constant direct current voltage control station; locking the converter of the constant direct current voltage control station; disconnecting the wire-inlet switch of the alternating current side of each converter station; performing pole isolation of each converter station; and disconnecting the charging resistor bypass switch or the switch of each converter station.