According to Official Guinness Records,
The most pull ups in one hour is 1,009 by Stephen Hyland (UK) in his home fitness center, Stoneleigh, UK, on 1 August 2010. Hyland completed 91 sets of eight repetitions, 20 sets of seven repetitions, six sets of nine repetitions, four sets of four repetitions, three sets of six repetitions, and one set each of 21, 12, 10, five, three and two repetitions.
For a complete list of 2010 records, please visit 2010 Guinness Records in United Kingdom.