Photons with very high energy up to TeV (VHE) emitted from active galactic nuclei (AGNs) provide some invaluable information of the origin of g-ray emission. Although 66 blazars have been detected by EGRET, only three low redshift X-ray selected BL Lacs (Mrk 421, Mrk 501, and 1ES 2344+514) are conclusive TeV emitters (PKS 2155-304 is a potential TeV emitter) since VHE photons may be absorbed by cosmological background infrared photons (external absorption). Based on the “mirror” effect of clouds in broad line region, we argue that there is an intrinsic mechanism for the deficiency of TeV emission in blazars. Employing the observable quantities we derive the pair production optical depthobs due to the interaction of VHE photons with the reflected synchrotron photons by electron Thomson scattering in broad line region. This sets a more strong constraints on very high energy emission, and provides a sensitive upper limit on the Doppler factor of the relativistic bulk motion. It has been suggested to distinguish the intrinsic absorption from the external by the observation on variation of the multiwavelegenth continuum.