F-logic language is a logic database language based on frame logic．It is powerful in expressing object-oriented features．However，there was little work in discussing its capability of manipulating complex objects．In this paper，the authors compare the capability of F-logic with that of logic database languages represented by COL (complex object language)．Through tWO pairs of semantic preserving transformations，F-logic programs and their Herbrand interpretations can be transformed into COL programs and their corresponding Herbrand interpretations，and vice versa．Also，the effects of negation are discussed．The results of this paper indicate that，without consider-ation of the effects of OID generating，F-logic language has the same power in manipulat-ing complex objects as COL, LDL1(1ogic database language), and ELPS．