  With a recently constructed composite quasar spectrum and the \chi^2
minimization technique, we demonstrated a general method to estimate the
photometric redshifts of a large sample of quasars by deriving the theoretical
color-redshift relations and comparing the theoretical colors with the observed
ones. We estimated the photometric redshifts from the 5-band SDSS photometric
data of 18678 quasars in the first major data release of SDSS and compare them
with the spectroscopic redshifts. The redshift difference is smaller than 0.1
for 47% of quasars and 0.2 for 68 % of them. Based on the calculation of the
theoretical color-color diagrams of stars, galaxies and quasars in both the
SDSS and BATC photometric systems, we expected that with the BATC system of 15
intermediate filters we would be able to select candidates of high redshift
quasars more efficiently than in the SDSS, provided the BATC survey could
detect objects with magnitude fainter than 21.
