The vortex core model can keep the convergence in the limit state by setting the model angle conditions so as to improve the model of straight vortex line segment induced velocity calculated by the Biot-Savart law at every point. The model of the blade is simulated by Weissinger-Llifting-surface theory, while PIPC algorithm and CB2D algorithm are used to solve the rotor free-wake. The models and algorithms above are then combined to numerically calculate the wake of certain rotor. The results show that the radial displacement of tip vortex calculated by the improved vortex core model contracts remarkably. This is closer to the actual situation than previous model. In addition, the result of free-wake calculated by the improved vortex core model agrees with the experimental data perfectly. Therefore, the improved free-wake model of rotor is more accurate than the original one.