In order to forecast the mining process of oil and gas field rightly, simulate the flow process of reservoir fluid accurately and reveal the fluid distribution law, it must be considered that multiphase fluid seepage caused by water injection and exploitation, the change of stress state and the coupling between the reservoir deformations. According to the basic theory of rock mechanics, fluid mechanics in porous medium, geologic mechanics, calculated mechanics and fluid-solid coupling seepage, a mathematical and numerical model of seepage field and stress field coupling is developed in porous medium and a computer program is designed with the method of finite element technique. The Coupling Law of depressurizing exploitation Seepage field /Stress field in porous medium is studied. By the method of numerical simulation the variation law of stress-strain with time and space around borehole of impermeable rock medium, variety law of rock physical properties parameters is studied. Results show that the quantity of change nearby oil well and the change gradient is bigger, so it reduces very quickly to the oil deposit boundary,the stress and the strain are also biger in the oil well control area's influence area.