To examine the integration capability of candidate schemes under the condition of uncertainty, the probability multiple-criteria decision-making (MCDM) method, which is based on interval number analytic hierarchy process (AHP) and the robust design (RD), has been introduced to the effectiveness evaluation of aircraft conceptual/preliminary scheme, and the evaluation method of the Efficiency Practicability of Aircraft Conceptual/Preliminary Scheme (EPACS) has been founded. At first, the basic definition and correlative mathematics model of EPACS was made up. And then, taking into account of the correlation of all design/state variables in aircraft scheme, the structural model and the evaluation flow of EPACS was established. At last, the feasibility and validity of the above analysis had been proved by some examples.