  We introduce the idea of {\it effective} dark matter halo catalog in $f(R)$
gravity, which is built using the {\it effective} density field. Using a suite
of high resolution N-body simulations, we find that the dynamical properties of
halos, such as the distribution of density, velocity dispersion, specific
angular momentum and spin, in the effective catalog of $f(R)$ gravity closely
mimic those in the $\Lambda$CDM model. Thus, when using effective halos, an
$f(R)$ model can be viewed as a $\Lambda$CDM model. This effective catalog
therefore provides a convenient way for studying the baryonic physics, the
galaxy halo occupation distribution and even semi-analytical galaxy formation
in $f(R)$ cosmologies.
