Abstract: Wireline formation test is one of the most direct ways to determine the fluid properties of the target strata and evaluate reservoirs. Formation Evaluation Tool is a new homemade formation evaluation system. It can not only test the formation pressure accurately, and determine formation fluid type and gasoil-water contacts using pressure profile, but also pump the mud filtrate and monitor real time formation fluid characteristics while sampling in the target strata, which plays an important role in determining formation fluid properties and analyzing fluid components. At the same time, it can also calculate the formation per-meability and predict the productivity of the reservoirs. Through the successful application in Bohai oilfield, the principles and main purpose of FET were introduced briefly, its advantages and limitations and typical successful examples of the application were described in detail in this paper, which popularize the applica-tion of FET in other oilfields.