  The studies and constraints on the emission region are crucial to the blazar
radiation mechanism. Yet the previous works mainly focus on individual sources.
In this work, we make use of the largest and the latest spectral energy
distribution (SED) fitting results in the literature to statistically study the
blazar emission region property in the framework of leptonic one-zone. Our
results reveal (1) FSRQs show lower electron energy ($\gamma_{\rm p} \lesssim
1.6 \times 10^{3}$) than BL Lacs and tend to have a stronger magnetic field
($B$) and smaller electron-to-magnetic energy ratio ($U_{\rm e}/U_{\rm B}$)
than BL Lacs; (2) we find the electro-magnetic equipartition would rather
happen in the jets of BL Lacs than happen in the jets of FSRQs; (3) there are
682 blazars with a magnetic field weaker critical value of generating the
Kelvin-Helmholtz instability, thus one-third of the blazars in our sample are
able to produce this instability; (4) the distance ($d_{\rm em}$) between the
emission region and the central black hole (BH) is in the scale of $\sim$0.1
pc, the location of the emission region may be evenly distributed inside and
outside the broad line region (BLR).
