A great many researches indicate that amino acids, sugars, and lipids are precursors of aroma compo- nents of ester, and synthesis courses of the compo- nents had been clear. Alcohol acyltransferases (AATs) and alcohol dehydrogenases (ADHs) are key enzymes. Firstly, the amino acids, sugars, and lipids are trans- formed into acids, aldehydes or alcohols, and then into esters. In these reactions, the transformations from acids and alcohols to esters could be catalyzed by AAT directly, while the aldehydes should be trans- formed into acids or alcohols, consequently, into esters. Furthermore, the transformations between al- dehydes and alcohols need participation of ADH, which provide precursors of esters and other components of aroma (Yamashita 1977; Charles 2000). AATs are key enzymes of esterification of alcohol, and the kind of substrates determine the products of ester. Through parallel biochemical analysis of AAT and PTR-MA to volatile of strawberry, some relationship between ex- pression of AAT gene, AAT capacity and involved esters were found (Carbone 2006). Someone designed 12 crosses to study genetic trends of rice aroma, and suggested that some hybrids’ aroma were controlled by complement of two recessive genes, some were controlled by dominant genes, and some genes inhibited the formation of aroma (Mahalingam et al. 2005; Kole 2005; Dartey et al. 2006)