5-Bromo-2-(5'-bromo-2'-hydroxyphenyl)benzoxazole 4 is prepared from the Sandmeyer reaction of 5-amino-2-(5'-amino-2'-hydroxyphenyl)benzoxazole 3 with copper bromide. Two kinds of the (hydroxyphenyl)benzoxazole compounds are investigated for application in fluorescent probe sensing amino compounds and compound 4 is proved to be more suitable for sensing haxamethylenediamine and hydrazine with different fluorescent colors.