Guidi, ranked 394th in the world, faced one of archery's brightest stars in South Korea's Im Dong-hyun, who broke the world record for 72 arrows on Friday and won bronze in the team event on Saturday.
Im was seeded first of 64 competitors after scoring 699 from a possible 720 in the ranking round, while Guidi was ranked last, notching 110 points fewer.
Korea's world number two made short work of the 42-year-old Guidi, who got off to a good start but failed to put Im under any pressure in the individual competition's new set-based format.
"I am still shaking. Did you see me shaking on the shooting line?" he asked. "I had nothing to lose today. My first objective was being here and I am," Guidi said.
"I just hope I did not make such a bad performance."
Myanmar's Nay Myo Aung, ranked 56, and Egyptian Ahmed El-Nemr, 57, pulled off the biggest shocks of the first round by eliminating Romain Girouille who was seeded ninth after Friday's ranking round, and Canada's Crispin Duenas, ranked eight.
However, the success was fleeting as both went out in the next round.
On the women's side, Taiwan's Tan Ya-ting looks to be one of the few real challengers to South Korea's team gold medal-winning trio of Ki Bo-bae, Lee Sung-jin and Choi Hyeon-ju, who shoot later in the week.
Mexican Aida Roman also made it through her opening two matches, though her second round opponent Bombayla Devi Laishram could hardly have made it easier for her.
The erratic Indian missed the scoring rings completely with her first arrow of the fourth set, then hit dead centre for 10s with the other two.