  We consider the general problem of derivation of the Feynman rules for the
matrix elements in momentum representation from the given Lagrangian in
coordinate space invariant under the transformation of some gauge group. LanHEP
package presented in this paper allows to define in a convenient way the gauge
model Lagrangian in canonical form and then to generate automatically the
Feynman rules that can be used in the following calculation of the physical
processes by means of CompHEP package. The detailed description of LanHEP
commands is given and several examples of LanHEP applications (QED, QCD,
Standard Model in the t'Hooft-Feynman gauge) are presented.
