β-amylase proteins (BAM) are important to many aspects of physiological process such as starch degradation. However, little information was available about theBAMgenes inAnnona atemoya, an important tropical fruit. SevenBAMgenes containing the conservative domain of glycoside hydrolase family 14 (PF01373) were identified withAnnona atemoyagenome, and theseBAMgenes can be divided into four groups. Subcellular localization analysis revealed thatAaBAM3andAaBAM9were located in the chloroplast, andAaBAM1.2was located in the cell membrane and the chloroplast. TheAaBAMsbelonging to Subfamily I contribute to starch degradation have the higher expression than those belonging to Subfamily II. The analysis of the expression showed thatAaBAM3may function in the whole fruit ripening process, andAaBAM1.2may be important to starch degradation in other organs. Temperature and ethylene affect the expression of majorAaBAMgenes in Subfamily I during fruit ripening. These expressions and subcellular localization results indicating β-amylase play an important role in starch degradation.