Thorpe's Olympics bid fails at Australian trials
The five-time Olympic champion, who quit competitive swimming in 2006 and only returned to pool late last year, ranked 21st in the 100m freestyle with a time of 50.35 seconds.
Only the top 16 advance to the semifinals, and world champion James Magnussen led the qualifiers with a time of 48.26.
Earlier, Thorpe failed to reach the final of the 200m freestyle, which was considered his best chance of qualifying for London 2012, finishing 12th out of the 16 semi-finalists.
Thorpe needed to finish first or second in the 100 or 200m to earn individual selection for the London Olympics, or place in the top six in either event to be considered for a selection as a relay swimmer.
Thorpe won five Olympic gold medals, 11 world championships and set13 world records after bursting onto the scene in 1999.
He was the most globally recognized swimmer until American Michael Phelps emerged.