Negotiating the 207km from Asco to Manresa, Simon powered home in a time of 4:58.27 to secure an impressive stage win.
With just 23km to go, a bunch sprint finish ensued with Simon having just enough to pip Rigoberto Career of Colombia and Sylvester Szmyd of Poland.
Spaniard Samuel Sanchez finished in fourth spot, while Dario Cataldo of Italy took fifth from Jurgen van den Broeck and Michael Albasini.
Meanwhile, Swiss rider Albasini consolidated his position at the top of the general classification.
Julian Simon (Saur-Sojasun)
Rigoberto Career (Sky Team)
Sylvester Szmyd (Liquigas-Cannondale)
Samuel Sanchez (Euskaltel Euskadi)
Dario Cataldo (Omega Pharma-Quick Step)
1. Michael Albasini (Green Edge)
2. Jurgen van den Broeck (Lotto Belisol)
3. Daniel Martin (Garmin Barracuda)
4. Samuel Sanchez (Euskaltel Euskadi)
5. Rigoberto Uran (Sky Team)