Federer meets the Ukrainian later today in Shanghai after dispatching Diego Schwartzman in the second round.
Federer looked good in his 7-6 6-4 victory and will be hoping for more of the same today.
Dolgopolov beat Feliciano Lopez in the round of 32 and Jack Stock in the first round before booking his place against Federer.
Federer has won all four of their meetings for far but insists it won’t be a walkover today.
“I know Dolgopolov very well,” Federer said after his win over Schwartzman.
“We practised in Dubai a tonne the past few years so he’s a good guy. He’s always got good energy and he always shows it on the court.
“He’s had some issues with his injuries lately, like at Wimbledon he retired against me but I think this court is perfect for him, you know.
“The slider on his serve must work very well here and then he returns very fast and deep.
“So it’ll be a tough test for me.”
Federer, who has won two Grand Slams and five titles this year, is looking to end the season on a high.
He is hoping to claim another couple of titles with the ATP Tour Finals in London coming next month.
“I’m playing mostly, you know, only the big tournaments now, so you need to be really tip-top shape and ready to go, and it’s just not so simple,” said Federer on adding to his title haul.
“I couldn’t be happier with the season, to be quite honest. I’m relieved that I’m feeling better since the American summer, you know, and Canada.
“Just happy being here now and hopefully, to play a good season. It would be nice to pick up one more title, maybe a couple more, would be nice, and then get into training and start again next year and then get more chances next year.”