Zhou made his debut with the Swiss-based team last season and the extension should finally give him a chance to race in front of his home fans.
The Chinese Grand Prix in Shanghai is scheduled for April 21 after a five year absence due to the COVID-19 pandemic and subsequent restrictions.
"Signing again with the team is always a great feeling, especially when we know how things are shaping up," said Zhou in a team statement ahead of the Singapore Grand Prix.
"My relationship with Valtteri is really good, and we are working closely together and with the team to push everyone forward.
"I am also very excited about the opportunity to finally race with my team in China, in front of my home crowd. It will be a great moment and I’m proud to be able to share it with all those who have supported me."
Alfa Romeo are run by Sauber and will become the factory Audi team from 2026.
Bottas, a previous race winner with Mercedes, already had a contract for 2024 as part of a multi-year deal that runs to the end of next year.
"There is a good atmosphere within our squad, I get along with Zhou and we both push each other hard to improve," said the experienced Finn.
"There is an impressive amount of work going on behind the scenes, in Hinwil and beyond, and now that the lineup is set for next year, we can focus fully on improving."
Formula Two championship leader Frenchman Theo Pourchaire will continue to be the team's reserve driver.
