  The self-energy effect on the neutron-proton (np) pairing gap is investigated
up to the third order within the framework of the extend Bruecker-Hartree-Fock
(BHF) approach combined with the BCS theory. The self-energy up to the
second-order contribution turns out to reduce strongly the effective energy
gap, while the \emph{renormalization} term enhances it significantly. In
addition, the effect of the three-body force on the np pairing gap is shown to
be negligible. To connect the present results with the np pairing in finite
nuclei, an effective density-dependent zero-range pairing force is established
with the parameters calibrated to the microscopically calculated energy gap.
