The atmospheric turbulence probing source of adaptive optics (AO) is proposed by the promotion of beacon (namely guide star, GS). However the unavoidable anisoplanatic error it brings can degrade the performance of AO system. Taking account of the differences of height location and spatial angular deviations between GS and object, the ensemble statistical characteristics of anisoplanatic error with different GS modes are investigated by numerical modeling, including natural guide star (NGS) and laser guide star (LGS). In NGS mode, the effective angular anisoplanatic variance is smaller than the traditional evaluation value (θ/θ0)5/3. So the conventional characterization of the angular anisoplanatic degradation in AO correction with atmospheric anisoplanatic angle θ0 is more serious than actual circumstance. In LGS mode, the higher the beacon probing altitude is, the smaller the Zernike aberration modal anisoplanatic error is. But the aberration modal correlation degradation between LGS and object resulted from their angular deviation becomes more sensitive. Under such circumstance the AO system operation mode and the GS mode should be weighed up and optimized according to practical application. The numerical results provide theoretical support for the experiment investigation of atmospheric AO with LGS in future.