After　defining　the　idea　of　Convert　channel,　this　paper　analyses　detecting　methods　of　convert　channel　including　syntactic　information　flow　analysis　and　semantic　information　flow　approach.　This　paper　put　forwards　one　method　of　improved　syntactic　information　flow　processing　whose　core　idea　is　to　design　PC　to　sign　every　row　of　program　in　this　kind　of　method,　and　detect　the　covert　information　flow　by　this　kind　of　data　structure　-　stack.　The　validity　of　this　method　is　proved　using　an　example　in　this　paper.　©2010　IEEE.