Hughes said: "On a football level Ji is someone I have admired from afar for years.
"He wore the red shirt of Manchester United in a distinguished way and he will bring a great deal to the team, I can't wait to start working with him.
"Ji is a motivated guy, he feels there is success ahead of him, he ticks every box. It's a very exciting time for QPR.
"He's very adept in a number of positions. What he brings to the team is technical ability, a huge work ethic and a winning mentality.
"He understands what it takes to win trophies and to win matches, and I want to take that from Ji and pass it to the rest of the team.
"I said at the end of the season we didn't want to be in the same position next season and I stand by that, we are in a better place now."