provide very important constraints for the theoretical models, which are used to explain the high-energy radiation from rotation powered pulsars. The observed data is so rich that the local properties in the magnetosphere, e.g. retarded relativistic effect, the time of flight, the strength of the local magnetic field, the local radius of curvature, the local soft photon density etc., are necessarily to be used in order to explain the observed phase-dependent spectra and energy-dependent light curves from pulsars. These local properties associated with the observed photons not only depend on the global pulsar parameters, i.e. rotation period and surface magnetic field, but also depend on the angle between the magnetic axis and the rotation axis (the inclination angle $\alpha$) as well as the viewing angle ($\zeta$).

EGRET has observed the phase-resolved emission characteristics such as pulse profiles and phase-resolved spectra of Crab, Vela and Geminga Pulsars (Thompson et al. 1996). Fierro et al. (1998) have divided the observed photons of the Crab pulsar in the energy range from 100 MeV to 10 GeV into eight different phase bins and have shown that the spectra of each phase bin is very different. If a power-law fitting is used, the spectral indices 