  We constructed a sample of 185 Flat Spectrum Radio Quasars (FSRQs) by
cross-correlating the Shen et al.'s SDSS DR3 X-ray quasar sample with FIRST and
GB6 radio catalogues. From the spectrum energy distribution (SED) constructed
using multi-band (radio, UV, optical, Infrared and X-ray) data, we derived the
synchrotron peak frequency and peak luminosity. The black hole mass and the
broad line region (BLR) luminosity (then the bolometric luminosity) were
obtained by measuring the line-width and strength of broad emission lines from
SDSS spectra. We define a subsample of 118 FSRQs, of which the nonthermal jet
emission is thought to be dominated over the thermal emission from accretion
disk and host galaxy. For this subsample, we found 25 FSRQs having synchrotron
peak frequency > 10^{15} Hz, which is higher than the typical value for FSRQs.
While only a weak anti-correlation is found between the synchrotron peak
frequency and peak luminosity, it becomes significant when combining with the
Wu et al.'s sample of 170 BL Lac objects. At similar peak frequency, the peak
luminosity of FSRQs with $\nupeak > 10^{15}$ Hz is systematically higher than
that of BL Lac objects, with some FSRQs out of the range covered by BL Lac
objects. Although high $\nupeak$ are found in some FSRQs, they do not reach the
extreme value of BL Lacs. For the subsample of 118 FSRQs, we found significant
correlations between the peak luminosity and black hole mass, the Eddington
ratio, and the BLR luminosity, indicating that the jet physics may be tightly
related with the accretion process.
