Abstract: A synthesis of flavanones was provided, that a series of substituted cinnamic acid reacted with 2,4,6-trihydroxy pyrimidine,catalyzed by phosphorus oxychlorid and aluminum chloride (anhydrous). It could directly obtained series of novel diazinflavanones such as 5,7-dihydroxy-2'-chlor-diazin-flavanone. Their structures were confirmed by IR、1H NMR、MS and elemental analysis. The preliminary biological test indicated that most of these compounds had good fungicidal activity.