The Polish number one has been in impressive form at Melbourne Park, cruising into the last eight with a comfortable win against Ana Ivanovic on Sunday.
Radwanska beat Li on the way to winning the Sydney International earlier this month but believes that her Chinese opponent will provide the biggest test of her tournament to date.
She told reporters: "It's always tough against her. She's always playing very solid tennis.
"I think I really have to play aggressive against her, definitely serving good, really playing my hundred percent best tennis.
"Otherwise I'm not going to win. She's a very consistent player and moving very well. I think in our matches it's not about the power on the serve."
The fourth seed has not dropped a single set in her last 13 competitive matches.