Strongasymmetricalvorticesappearontheleewardofslenderbodyathighanglesofattack,whichhasveryunfavorableeffectonthestabilityandcontroloftheaircraft.Amethodisdevelopedtocontrolthesideforceofslenderbodyathighanglesofattack,andisverifiedinwindtunnel.Athin-filmtriangularself-excitedoscillationflagisfixedatthetipoftheslenderbodymodelwhosesemi-apexangleis10°.Sideforceisapproximatelylinearlyproportionaltoroll-settingangleofself-excitedoscillationflagathighanglesofattack,andtheslopoffittingstraightlineobtainedbytheleastsquaremethodis-0.158.Thelinearrelationshipbetweensideforceandroll-settingangleprovidesconveniencefordevelopingsideforcecontrollawofslenderbodyathighanglesofattack.Experimentaldatashowsthatthesideforcecoefficientsvarylinearlywithroll-settingangleswhenaspecificplasticself-excitedoscillationflagisusedasthecontrolflag.Therangeofsideforcecoefficientandroll-settingangleare,respectively,-3.2to3.0and-20°to20°.Thedeviceissimple,effective,andisofgreatpotentialinengineeringapplication.