The last paper has introduced the O—Datalog，a deductive query language of the object—oriented database system FOOD．This paper puts great emphasis on dis-cussing some transformations of the O—Datalog programs，and proving that these trans-tormations preserve the same semantics．So an O—Datalog program can be transformed into a corresponding Datalog program and can be evaluated using the Datalog program，then an algorithm of evaluating the O—Datalog programs is given．