  BL Lacs are one subclass of blazars with highly energetic $\gamma$-ray
emission, which is strongly boosted by a relativistic beaming effect. The
latest catalogue of the 10 years of {\it Fermi}/LAT data Abdollahi et al.
(2020) and the $\gamma$-ray Doppler factors in Pei et al. (2020) provide us
with a large BL Lac sample to study their jet emission morphologies and
intrinsic properties. In this paper, we collected a sample of 294 {\it Fermi}
BL Lacs and probed the correlations between the $\gamma$-ray emissions and
luminosity distances. Our analyses give following conclusions: (1) the observed
$\gamma$-ray emissions are really boosted by the $\gamma$-ray Doppler factor,
and the intrinsic $\gamma$-ray emissions are closely correlated with luminosity
distances. (2) the morphology of jet emissions for HBLs may be continuous,
while that for IBLs may be the case of a moving sphere in the $\gamma$-ray
bands.
