Abstract: prestressed fabricated PC frame structure as a new type of precast concrete structure，opened up new ways of industrial production of prestressed structures． In order to use this structure better in actual projects，the research on the ductility of the preloaded prestressed concrete frame structure and its beam ends moment amplitude-modulation capacity would have important theoretical significance and practical value． Based on a single-layer double span-frame structure，it was researched and analysed the moment amplitude-modulating coefficient values from the plastic hinge rotation capacity and crack width，whose results were in good agreement with the experimental results．