Abstract: This article points out that human can not avoid misoperations and puts forward an idea that the human factor and machine should be taken into account together in design.Through analysing defects and accidents occured in operation, the writer has put forward and performed a series of new "Anti-Misoperation disigns".Studying the "defect trees" we find out that the rate of defect, in this system has decreased considerablly and the safety, misoperation compatibility and reliablity have increased greatly. It has deen proved in practice that this design can reduce and avoid a lot of defects and dangers in flight.