The flow-field characteristics of propeller slipstream under different advance-diameter ratios were carried out by three-dimensional numerical simulation. The induced coefficient was used to quantify the slipstream effect; the slipstream characteristics were deeply explored on the basis of the vortex theory. Result showed that the accelerated effect of the slipstream increased firstly

and then decreased along the radial direction

while the twisted effect of the slipstream decreased along the radial direction; both the accelerated effect and the twisted effect decreased with the increment of the advance-diameter ratio; the flow-field of the propeller slipstream can be well described by the axial induced coefficient and circumferential induced coefficient with circumferentially averaged treatment as well as the vortex system structure.