Abstract: Based on previous studies and beginning with the basic pattern of percolation in abnormally high pressure deformation medium, this paper studies the influences of permeability decrease on percolation after the formation pressures near the well bottoms having dropped, the influences of start - up pressure gradient on percolation of fluids in reservoirs, and the influences of degassing on productivity when bottom hole producing pressure getting lower than crude saturation pressure. A new productivity model of abnormally high pressure oil reservoir with degassing effect considered is built to provide a theoretical basis for rational development of abnormally high pressure deformation reservoirs. This model is used to study productivity at different pressure drawdown of reservoirs, and the curve shows a distinct inflexion, therefore the optimized maximum producing pressure differentials under different average formation pressures can be determined.