Former Italian prime minister Silvio Berlusconi's 30-year ownership ended last April when he sold the club to Li's Chinese-led consortium for €740 million ($913m).
Since then, there have been questions about the financial stability of the consortium that subsequently went on a €200-million summer spending spree on new players.
"I'm very excited to say that today we are celebrating our first-year anniversary with the club," Li, 48, said in an open letter to fans published on the club's website.
"I'd like to take this opportunity to stress once again we are fully committed in this project for AC Milan's growth.
He continued: "Of course, we still have a long way to go to achieve our goal, which is to bring the club back to where it belongs: at the top of European football.
"While we are celebrating a positive first year, we know this is only the beginning of our project to make AC Milan successful and stable, a project we shall pursue aiming for excellence, and fully respecting all the financial commitments we undertook."
Coached by former AC Milan midfielder Gennaro Gattuso the club are currently sixth in Serie A and through to the Italian Cup final in May.