The assembly coordination accuracy of aircraft manufacturing becomes more and more strict with the development of the aircraft structure and process. So defining fairly aircraft components dimension to achieve process optimum through tolerance analysis is an inevitable trend. This thesis introduces and researches the basic theory

with applying selection of certain aircraft components datum. Defining datum is decided by function request

indicating transfer deviation by datum and datum consistency principia of aircraft components. The datum selection method can be applied to dimension design. Assembly quality is improved by defining fairly aircraft components datum

with reducing production cost and increasing productivity in some case.