Pyramid wavefront sensor (PWFS) has the advantages of high spatial resolution and light utility efficiency. To correctly extract slope information of the wavefront from the pupil images of PWFS, the dimension and position of the pupils should be calibrated in advance. The effects of the dimension and position calibration errors of the pupils on close-loop performance of adaptive optics system are investigated. The pupil calibration method of non-modulation pyramid wavefront sensor is proposed, and this method is verified by many times of simulated experiments under the conditions that system aberration and detection noise are considered. The simulation results show that the proposed method can calibrate the pupils accurately in the face of system aberration (its root mean square value is below 1.7λ). The method can be applied to the practical adaptive optics systems.