Abstract: In this paper, taking Daqing oil field as an example, as viewed from the stress field, it is indicated that waterinjection by high pressure not only decreases the effect ire stress, makes the fault activate, but also it may increase the horizontal stress and make the fault to be stable.#br#The in-situ absolute stress measurement shows that the original stress field was eontroled by normal fault and now the orientation of maximum principal stress changed to horizontal direction.In adout recent one year, the tensile pressure of layer in depth of 1000m was increased, and now the deformation and damage in injection-exbloitation casing tend to decreaes.It is showed that the fault began to be somewhat stable.#br#The tendency of development of the earthquakes by water injection in oil tield is similar to the induced earthquake of reservoir in that the process is from stability to unstability and even to sharpping state, then it is gradually recovered to the state of stability.This is a quite long process, and the time unit is 10 years.For high and arable production of an oil field, a method-suitable to the objective law should be used to reduce damages.