In order to decrease the weight of aircraft structural part effectively, face to the skeleton of aircraft, the author regards the conceptual design of structural part (such as strengthen frame, general frame and canard beam) as research content. By analyzing the concept of 'gradient threshold' and pointing out its weakness, the author proposes the concept of 'modified gradient threshold' and combines it with the strategy of 'constraint compensation' to form a new kind of topology optimization algorithm for structural layout of structural parts. The topology optimization results of multiple examples show that their layouts are very innovative and deserved to be studied in detail. So we can draw three conclusions. One is that using the combination of CAD/CAE and topology optimization for aircraft structural part above mentioned conceptual design is feasible. The other is that the proposed 'modified gradient threshold' topology optimization algorithm is effective. The last is that a new design approach with good operation which differ from conventional design method is constructed for structural part structure layout.
