Multi-terminal HVDC transmission technology using voltage source converters is suitable for integrating large off-shore wind farms. DC voltage stability is the main problem for coordinated control of Voltage Source Converter based Multi-Terminal High Voltage Direct Current (VSC-MTDC) transmission system. The fixed droop coefficient of the traditional droop control leads to poor flexibility under severe disturbance. On this basis, this paper proposes an adaptive droop control method. By detecting the DC voltage deviation and the power margin, the fuzzy logic control is intended to adjust droop coefficient adaptively. Simulation results in PSCAD/EMTDC show that the proposed adaptive droop control strategy can reduce DC voltage deviation caused by the transmission power change and improve system operating performance within the allowable power margin range. This work is supported by National Natural Science Foundation of China (No. 51607075).