  Using the sample of radio selected BL Lacertae objects (RBLs) and X-ray
selected BL Lacertae objects (XBLs) presented by Sambruna et al. (1996), we
calculated the luminosities of radio, optical and X-ray of each source and made
the statistical analysis among the luminosities at different wave-bands,
broad-band spectral indices from radio to X-ray ($\alpha_{\rm rx}$) and peak
frequencies ($\nu_p$). Our results are as follows: (i) there is a positive
correlation between radio luminosity $L_{\rm r}$ and $\alpha_{\rm rx}$ and a
negative correlation between $L_{\rm r}$ and $\nu_p$. High-energy peak BL Lacs
(HBLs) and low-energy peak BL Lacs (LBLs) can be distinguished very well, the
dividing lines are probably those of $\log {L_{\rm r}}=43.25$ (erg/sec) and
$\alpha_{\rm rx}>$(or $\leq $)0.75 for $L_{\rm r}$ - $\alpha_{\rm rx}$ plot and
those of $\log {L_{\rm r}}\leq 43.25$ (erg/sec) and $\log {\nu_p}>14.7$ for the
$L_{\rm r}$ - $\nu_p$ plot; (ii) there is a weak positive correlation between
optical luminosity $L_o$ and $\alpha_{\rm rx}$ and a negatively weak
correlation between $L_{\rm o}$ and $\nu_p$; (iii) there is no correlation
between X-ray luminosity $L_X$ and $\alpha_{\rm rx}$ or between $L_X$ and
$\nu_p$. From our analysis, we find that synchrotron radiation is the main
X-ray radiation mechanism for HBLs while inverse Compton scattering for LBLs.
