Living　organisms　control　the　growth,　genetics,　and　aberrance　behavior　by　regulating　different　gene　expressions.　The　interaction　of　differently　expressed　genes　is　the　connection　of　Construction　of　Gene　Net,　which　can　reveal　the　information　about　the　cancers.　The　gene　net　model　is　helpful　to　understand　the　essence　of　life.　In　this　paper,　we　put　forward　a　novel　method　to　forecast　gene　net　that　was　inducing　fuzzy　theory　firstly.　Firstly,　Permutation　test　was　used　to　identify　differently　expressed　genes　after　eliminating　noise　signal.　Then　the　importance　of　a　gene　in　classifying　the　normal　and　tumor　was　estimated　based　on　the　gene＇s　entropy.　In　detail,　Negative　Big　(NB),　Negative　Middle　(NM),　Negative　Small　(NS),　Zero　(0),　Positive　Small　(PS),　Positive　Middle　(PM),　Positive　Big　(PB)　7　ranks　were　introduced　to　sort　the　Different　Gene　Expression　values.　The　relations　between　two　genes　were　figured　by　seven　＇if-then-＇　rules　according　to　genes＇　expression　values.　In　conclusion,　we　invent　a　new　method　to　construct　fuzzy　gene　net　model　and　it　is　useful　to　comprehend　the　occurrence　and　development　of　tumor　and　cancer.　At　last,　MDM2-p53　Fuzzy　Gene　Net　was　succeeding　in　describing　the　relations　between　them.　©　2009　Binary　Information　Press.