[en] The program for calculating gamma quanta detection efficiency by coaxial Ge detector using the Monte-Carlo method in the energy range of 0.1-10 MeV for point and extended source is developed. The calculation algorithm takes into account the following processes of a γ quantum interaction with a matter: photoelectric effect, Compton effect, pair production, multiple scatteirng and bremsstahlung of secondary electrons, positron annihilation process, ionization electron losses. The program allows one to calculate spectrum of energy losses in the detector working volume and determine detection efficiency by the total absorption peak or by a peak related to one or two annihilation γ quanta escape. The results of efficiency calculation for several γ quanta energy values and for different mutual target-detector geometry are presented. The program is written in FORTRAN-4. The calculations are performed at the EC-1040 computer