  We propose that the majority of quasars at redshift $z\sim 1 - 5$ formed in
the environment of new born collapsed halos with 1-D velocity dispersion
$\sigma_v^{1d} \sim 400 \kms$. The harboring coefficient $f$ of quasars per
halo and the lifetime of quasars depend only on local process, not modulated by
the density inhomogeneities on scales larger than the size of the halos. Thus,
the bias of quasars on scale larger than the size of these halos is mainly
determined by the parameter $\sigma_v$ used for quasar environment
identification. With this model, the popular structure formation models, like
SCDM and LCDM, can be fairly well reconciled with the data of quasars,
including a. observed feature of the environment for quasars; b. redshift
evolution of quasar abundance; c. the two-point correlation functions of
quasars. This bias model predicts that the correlation function of quasars
doesn't significantly evolve, or only slightly increases with redshift.
