The invention discloses a control system and a control method for sending out offshore wind power through hybrid direct current, and the control method comprises the steps: unlocking an onshore converter station when the system is started, controlling the direct current voltage of the onshore converter station to be a first preset voltage value, then unlocking an offshore MMC converter valve, then starting a part of wind turbine generator sets, by reducing the direct-current voltage of an onshore converter station, after the direct-current voltage of an offshore DR converter valve is reduced to a preset voltage threshold, switching on the offshore DR converter valve to start to transmit direct-current power, starting the remaining offshore wind turbine generators, and controlling the direct-current voltage of the onshore converter station to be further reduced, so that the transmission power of the offshore DR continues to rise; therefore, all direct-current power is injected into the direct-current side through the offshore DR converter valve instead of the offshore MMC converter valve, loss of the small-capacity offshore MMC converter valve during long-term operation is reduced, economical efficiency is improved, overload of the offshore MMC converter valve is avoided, and safe and stable operation of the system is guaranteed.