The home movie features a man with more than a passing resemblance to the star and two women.
However, Simpson's lawyer, Yale Galanter, has branded the tape fake.
He told America's New York Daily News newspaper "While my client may appear fully clothed in portions of the tape, the man having sex is an impostor.
"This tape is garbage and we can prove it. O.J. wouldn't do anything like this." The man selling the film, David Hans Schmidt, stands by the claim that it is the sporting legend in the movie.
He said: "O.J. is welcome to say that's not him on the tape, just like he said he didn't murder Nicole Simpson and Ron Goldman but there's no question in my mind the real O.J. is having sex on this tape.
"When the tape comes out, people can make their own judgment." The release of the 25-minute adult movie comes almost 12 years to the day after the murders of Nicole Brown Simpson and Ron Goldman.
O.J. - who was accused of the killings - was later cleared of all charges.