Abstract: The time-varying disturbance problems are common in wind tunnel flow field control, the most typical of which is the disturbance of Mach number control caused by angle of attack in the transonic continuous sweep angle of attack test. In order to improve the accuracy of flow field control in the presence of time-varying disturbance, a novel feed-forward feedback composite control scheme is innovatively proposed. The feed-forward control is based on phase Lead Correction based Incremental Extend State Observer(LIESO), and the feedback control is based on the incremental Proportional-Integral(PI) control. The research on the transonic continuous sweep angle of attack test in the 1.2 m trans-supersonic wind tunnel is carried out to verify the composite control method. The test results show that: the LIESO + PI composite control method has remarkable effect on time-varying disturbance suppression, and good robustness, good adaptability to different model blockage and test Mach numbers, and has good engineering application value.