Effects of tip slots on the aerodynamic characteristics of helicopter rotor were investigated numerically by solving three-dimensional Navier-Stokes equations based on unstructured overset grids algorithm.Improved delayed detached eddy simulation (IDDES) based on the Spalart-Allmaras turbulence model and adaptive grid refinement technique were employed.Several slots in the rotor blade tip were designed on the base of Caradonna-Tung rotor to study the effect of tip slots.Numerical results show that tip slots are able to introduce the airflow from the leading edge and t it in the spanwise direction to be ejected out of the face at the rotor blade tip, which can reduce the strength of the rotor blade tip vortex and accelerate the dissipation process.Although tip slots may lead to the decrease of airfoils’lift coefficient at the root of the rotor blade, it can increase the lift coefficient of airfoils at the rotor blade tip, so the lift of the rotor with tip slots is almost the same as that of the rotor without tip slots.In addition, tip slots can also reduce the intensity of the tip shock wave, which is beneficial to reduce the wave drag of the rotor.