The 53-year-old was shown clips of her late brother's rehearsal for the song 'Bad' in the film on TV show Access Hollywood when she made the admission.
She said: "I have no plans to see it. It's a bit too soon for me. It really is."
However, the star expressed pleasure at seeing "the love and the joy that he gets out of when he performs". She also cited Michael's mentorship of up-and-coming dancers starring in the feature-length film, which is comprised of rehearsal footage from his scheduled comeback tour at London's O2 arena.
La Toya added: "I am pleased to see him mentoring, but I do know, however, Michael likes everyone to see him at his best and this is not a full-out rehearsal for him.
"There's so much more to him. The energy he puts behind him, I do not see it there. But it's good to have that as a memory as well."
This Is It will debut in cinemas on Wednesday, October 28 and is predicted to become the highest grossing concert film of all time.