A set of technology of numerical simulation for rotor flow field based on WENO (weighted essentially non-oscillatory)-piecewise linear scheme is developed to reduce the numerical dissipation of tip vortex caused by the second-order JST scheme. The moving overset grid method is selected to generate the grid system, the Navier-Stokes equation is selected to be the main control equation. In order to capture the flow details including the tip vortex more effectively, we use the seventh-order Roe-WENO scheme on the cartesian background grid, and the second-order Roe-piecewise linear scheme is adopted on the unstructured body fitted grid of blade. Temporal discretization method chooses the efficient dual-time implicit LU-SGS (lower upper symmetric Gauss-Seidel) scheme for time advancement. Finally, we use the method to numerically calculate the flow field of C-T(caradona-tung) model rotor in hover and the Helishape 7A model rotor in hover, and the comparison between the numerical results and the experimental data are good. Then we compare the results of WENO-piecewise linear scheme with the results of JST scheme. The comparison results verify the effectiveness of the WENO-piecewise linear scheme to calculate the flow field of rotor. And the results show that under the same calculation conditions, the proposed method can capture the flow characteristics of the rotor flow field more effectively, indicating that the WENO-piecewise linear scheme has lower numerical dissipation than the traditional second-order JST scheme when calculating the rotor flow field.