In this paper,the control characteristic of cascaded hybrid high voltage direct current (HVDC) system is studied. The influence mechanism of modular multilevel converter (MMC) inverters to the whole hybrid HVDC are investigated,and the complete voltage-current characteristic curves of the hybrid HVDC are obtained in droop control modes. Compared with the master-slave control,MMCs in droop control have ability to control both DC voltage and DC power,and the power reverse transmission will not occur. However,MMCs in droop control cannot control DC voltage accurately. Thus,an adaptive droop control strategy of cascaded hybrid HVDC system is proposed. The droop curve can be moved in real time adaptively according to DC current,which avoid the fluctuations of DC voltage due to the change of DC current. Finally,the simulation results verify the effectiveness of the proposed strategy based on PSCAD/EMTDC. This strategy can adjust the droop curves adaptively and realize accurate control of DC voltage in hybrid HVDC system,which improves the stability of the hybrid HVDC system.