  GeV gamma ray is an important observation target of DArk Matter Particle
Explorer (DAMPE) for indirect dark matter searching and high energy
astrophysics. We present in this work a set of accurate instrument response
functions of DAMPE (DmpIRFs) including the effective area, point-spread
function and energy dispersion that are crucial for the gamma-ray data analysis
based on the high statistics simulation data. A dedicated software named DmpST
is developed to facilitate the scientific analyses of DAMPE gamma-ray data.
Considering the limited number of photons and the angular resolution of DAMPE,
the maximum likelihood method is adopted in the DmpST to better disentangle
different source components. The basic mathematics and the framework regarding
this software are also introduced in this paper.
