In water-bearing gas reservoir development by using horizontal well mode, fluid inflow through perforation may produce remarkable effect on horizontal flow due to complex two phase seepage rule and special flow state of horizontal well, which may result in the change of pressure drop in fluid flow. In order to research flow pattern and pressure drop distribution regularity of two phase flow in horizontal well, established is a pressure drop calculation model for horizontal gas/water well and a liquid drop carrying model for horizontal gas well and applied is the fluent fluid simulation software to simulate the gas/water two phase mixing flow in horizontal well. Research results show that friction pressure drop, perforation roughness pressure drop and mixing pressure drop will increase along with increase of main flow velocity, well diameter increase can decrease friction pressure drop and perforation roughness pressure drop, fluid viscosity affects perforation roughness pressure drop only, viscosity increase may make the roughness pressure drop increase. Numerical simulation results show that flow rate and flow velocity increase from inlet to the outlet, perforation inflow will produce pressure drop, which comply with the principle of wellbore flow pressure drop.