The invention discloses a hybrid DC transmission-based fan grid-connected system. In the operation process of an existing hybrid direct-current system, fluctuation of an inverter side DC voltage is caused by fluctuation of a network voltage, so that fluctuation of a DC is caused and a commutation failure of an LCC is easily caused. The hybrid DC transmission-based fan grid-connected system comprises a rectifier station, an inverter station, a DC line and a wind turbine generator, wherein the rectifier station comprises a modular multilevel converter MMC, a rectifier side DC reactor and a rectifier side transformer; the inverter station comprises the line commutation converter LCC, an inverter side DC reactor and an inverter side transformer; the hybrid DC transmission-based fan grid-connected system is characterized in that the modular multilevel converter MMC is controlled by a stator module capacitor voltage and a constant DC at a DC side; and a permanent magnet direct-drive fan is controlled by a low voltage drop power. According to the hybrid DC transmission-based fan grid-connected system, a DC increase is suppressed by virtue of a constant DC control of the MMC and low voltage drop power control of the fan; and the probability of the commutation failure of the hybrid DC is reduced.