  The diffuse Galactic $\gamma$-rays from EGRET observation shows excesses
above 1 GeV in comparison with the expectations from conventional Galactic
cosmic ray (CR) propagation model. In the work we try to solve the "GeV excess"
problem by dark matter (DM) annihilation in the frame of supersymmetry (SUSY).
Compared with previous works, there are three aspects improved in this work:
first, the direction-independent "boost factor" for diffuse $\gamma$-rays from
dark matter annihilation (DMA) is naturally reproduced by taking the DM
substructures into account; second, there is no need for renormalization of the
diffuse $\gamma$-ray background produced by CRs; last but not the least, in
this work our new propagation model can give consistent results of both diffuse
$\gamma$-rays and antiprotons, by directly adding the signals from DMA to the
diffuse $\gamma$-ray background. This is a self-consistent model among several
possible scenarios at present, and can be tested or optimized by the
forthcoming experiments such as GLAST, PAMELA and AMS02.

Astrophysics;High Energy Physics - Phenomenology