Michal Kwiatkowski (Sky) won the race in a five-up sprint ahead of Tony Gallopin (Lotto Soudal) and Bauke Mollema (Trek-Segafredo), while Van Avermaet came home 38 seconds down in a chasing group.
"The top 10 was an objective and I achieved it," Van Avermaet said afterwards, according to RTBF. "6th place would have been possible, but Alberto Bettiol slipped away from our group in the final kilometres, and then I made an error in the final sprint. But I'm happy with 8th place. The sensations and the legs were good. I was on a good day."
Winner of Paris-Roubaix, Gent-Wevelgem and E3 Harelbeke in the spring, Van Avermaet rode a low-key Tour de France, though he placed second to Michael Matthews in the uphill sprint finish in Rodez.
A year ago, Van Avermaet emerged from the Tour with the form that carried him to the gold medal at the Rio 2016 Olympics road race. The Belgian will aim to be to the fore in the weeks to come at the BinckBank Tour, the WorldTour races in Montreal and Quebec and the World Championships in Bergen.
"Normally, I always come out of the Tour de France very well, but I was a bit sick during the last week this year and I came here with a few question marks," Van Avermaet said. "The last climb in the finale was a bit hard for me, but I knew that beforehand from having ridden here other years. But it all depends on the race situation and the number of riders who attack on the climb.
"I think I was on the same level as I was at this period last year, and I feel ready for the next races."