Chinese 12th seed Zheng Qinwen came from a set down to beat unseeded Russian Anna Kalinskaya at the Australian Open on Wednesday, setting up a semi-final clash against Ukrainian qualifier Dayana Yastremska.

The 21-year-old, known to her fans as "Queen Wen", had never progressed beyond the quarter-finals in eight previous Grand Slam appearances but held her nerve to win 6-7 (4/7), 6-3, 6-1 in two hours and 20 minutes.

"In the first set we had a big competition and the match was really tough for me," she said.

"I just told myself to stay focused, not to think anymore about the first set and I'm so happy right now, like really excited."

The players secured two breaks apiece in a tight first set on Rod Laver Arena but neither was able to make a decisive move and it went to a tie-break, where Kalinskaya dug deeper.

The Russian won 41 points in the opener – just one more than Zheng.

The match followed a similar pattern in the second set, with nothing to separate then until Zheng broke in the eighth game when Kalinskaya dumped a forehand into the net.

Zheng sealed the set in the next game with an ace.

The Chinese star broke twice to lead 4-1 in the deciding set as the match quickly drifted away from Kalinskaya, who received treatment to her right leg during a medical timeout.

It proved to be a temporary stay of execution for the 25-year-old, who lost the final two games to sink to defeat.

Victory means Zheng will move into the top 10 for the first time when the rankings are published after the Australian Open.

"That's good news for me, another motivation and especially I said last year at the Australian Open I wanted to be top 10 and one year later I'm here," she said. "It's an amazing moment." (AFP)