  The discovery of doubly heavy baryon provides us with a new platform for
precisely testing Standard Model and searching for new physics. As a
continuation of our previous works, we investigate the FCNC processes of doubly
heavy baryons. Light-front approach is adopted to extract the form factors, in
which the two spectator quarks are viewed as a diquark. Results for form
factors are then used to predict some phenomenological observables, such as the
decay width and the forward-backward asymmetry. We find that most of the
branching ratios for $b\to s$ processes are $10^{-8}\sim10^{-7}$ and those for
$b\to d$ processes are $10^{-9}\sim10^{-8}$. The flavor SU(3) symmetry and
symmetry breaking effects are explored. Parametric uncertainties are also
investigated.
