Theoretical calculations are achieved to study the effect of different deuterium pressures on various characteristics parameters for PF400J plasma focus using an international computer code.  Axial and radial velocities, voltage tube, plasma temperatures, and neutron yields at different operating deuterium pressures are computed. Neutron emission has been calculated in the device.  The maximum total neutron yield calculated is of the order of  and  neutrons per shot for entire pressure used. The computed results agree reasonably well with the published neutron yield curves.