  Hadronic production of the doubly charmed baryon $\Xi_{cc}$ ($\Xi^{++}_{cc}$
and $\Xi^{+}_{cc}$) is investigated under the general-mass
variable-flavor-number (GM-VFN) scheme. The gluon-gluon fusion mechanism and
the intrinsic charm mechanisms, i.e. via the sub-processes
$g+g\to(cc)[^3S_1]_{\bar 3}+\bar{c}+\bar{c}$,
$g+g\to(cc)[^1S_0]_6+\bar{c}+\bar{c}$; $g+c\to (cc)[^3S_1]_{\bar 3}+\bar{c}$,
$g+c\to (cc)[^1S_0]_6+\bar{c}$ and $c+c\to (cc)[^3S_1]_{\bar 3}+g$, $c+c\to
(cc)[^1S_0]_6+g$, are taken into account in the investigation, where
$(cc)[^3S_1]_{\bar 3}$ (in color {\bf $\bar 3$}) and $(cc)[^1S_0]_6$ (in color
{\bf 6}) are two possible $S$-wave configurations of the doubly charmed diquark
pair $(cc)$ inside the baryon $\Xi_{cc}$. Numerical results for the production
at hadornic colliders LHC and TEVATRON show that both the contributions from
the doubly charmed diquark pairs $(cc)[^1S_0]_6$ and $(cc)[^3S_1]_{\bar 3}$ are
sizable with the assumption that the two NRQCD matrix elements are equal, and
the total contributions from the `intrinsic' charm mechanisms are bigger than
those of the gluon-gluon fusion mechanism. For the production in the region of
small transverse-momentum $p_t$, the intrinsic mechanisms are dominant over the
gluon-gluon fusion mechanism and they can raise the theoretical prediction of
the $\Xi_{cc}$ by almost one order.
