Abstract: The designing research of the aeroscrvoelastic effects for a high performance aircraft using ACT is presented.The main purpose of this paper is to study the method of analysis and design of DFBW control system, while the structure modes of aircrft arc considered. The caulping equations which separate general equations into rigid and structure modes are ostabilished. Then the elastic transfer function of main internal loop of DFBW systems introduced for typical 1-st order longitudinal fuselage bending mode. Both the frequency response method and the optimal discrete outpul feedback regulator method are used in system design. A design example for the reference aircraft is iven.From research results, the recommended design criteria are (1)the peak point of interesting structure mode in LOG frequency characteristic plot should be placed below the 0-dB line for 12-dB at least to get a satisfactory attenuation of structure mode;and(2)the sensitivity of optimal (suboptimal) gain to the installed position of sensor may be used as a criterior of the degree of couiping effects of structure mode on the FCS.It is shown that the effects of structure mode on the FCS are not important, when Lhe sensitivity tends to zero.