It is well known that the problem of characterizing the automorphisms, in the category of abelian groups, with the extension property is resolved [1]. But in other categories, it is a very difficult problem. This paper extends the result in [1] to a category of modules. Let A be a unique factorization integral domain (UFD). Consider M a direct finite sum of cyclic modules over A where Ann A (M ) = {0} and α an automorphism of M . We give a necessary and sufficient condition such that α satisfies the extension property.