I think that he uses repitition to creat an emotional feeling
I feel Poe used the repetition i Annabel Lee as a mental echo for himself and the reader. The poem recalls a childhood memory for him, as if beckoning him to his past. As he recalls her, his language simplifies to that of a child or a more simple time, bringing in fantasy icons which would be familiar to a child from fairy tales or stories/fables. The repetition also represents a continued strong tie between Poe and Annabel Lee.