The　equation　of　motion　of　sandwich　beam　with　pyramidal　lattice　core　in　the　supersonic　flow　considering　geometric　nonlinearity　is　formulated　using　Hamilton＇s　principle.　The　piston　theory　is　used　to　evaluate　aerodynamic　pressure.　The　structural　aeroelastic　properties　are　analyzed　using　frequency-　and　time-domain　methods,　and　some　interesting　phenomena　are　observed.　It　is　noted　that　the　flutter　of　sandwich　beam　occurs　under　the　coupling　effect　of　low　order　modes.　The　critical　flutter　aerodynamic　pressure　of　the　sandwich　beam　is　higher　than　that　of　the　isotropic　beam　with　the　same　weight,　length　and　width.　The　influence　of　inclination　angle　of　core　truss　on　flutter　characteristic　is　analyzed.