The　dynamic　model　of　a　robot　arm　with　both　joint　flexibility　and　link　flexibility　is　developed　for　the　manipulation　of　a　constrained　object　based　on　the　absolute　coordinates.　The　forward　dynamic　model　is　derived　according　to　the　kinematic　and　dynamic　constraints　between　the　operated　object　and　environment.　When　the　desired　trajectory　of　object　and　its　contact　forces　with　environment　are　selected　as　boundary　conditions,　the　inverse　dynamic　model　is　developed.　A　reasonable　input　for　a　specified　task　can　be　obtained　from　the　proposed　inverse　model.　The　forward　dynamic　model　can　be　used　for　numerical　simulation.　The　advantage　of　the　new　method　is　illustrated　through　an　example　of　a　3R　robot　arm　with　joint　flexibility　and　link　flexibility.