Venus produced a string of errors in her match on Tuesday

The Wimbledon champion, seeded eighth, was broken to love serving for the match at 5-3 but her Chinese opponent, ranked 61, could not capitalise.

Russian second seed Svetlana Kuznetsova swept into the second round with a 6-3 6-1 win over France's Nathalie Dechy.

Kuznetsova had lost three of her four previous matches against Dechy but this time she overpowered her in 37 minutes.

Fourth seed Ana Ivanovic joined her in round two, easing to a 7-5 6-3 win over Romania's Sorana Cirstea.

And sixth seed Anna Chakvetadze also progressed when Andrea Petkovic retired hurt in the first game of their match.

Even if I'm not playing well, like I have always Plan B or I always can control myself. It's like I'm always there - I feel more consistent Svetlana Kuznetsova

Williams, posting her first victory at the Australian Open in three years after injury woes in 2007 and a first-round defeat in 2006, hit 29 unforced errors against Zi.

But she brushed off her problems, saying: "Errors happen, that's tennis, but I felt good out there and had a lot of fun. Got to hit a lot of balls, which I felt was good.

"She definitely made me play some balls that I wasn't expecting to come back. It was definitely challenging."

Kuznetsova, who will meet Bulgaria's Tsvetana Pironkova in the second round, has emerged as a serious challenger after reaching the 2007 US Open final.

Twelve months ago she had an unhappy time at Melbourne Park, tumbling out in the fourth round after suffering from a virus.

Petkovic could not continue after injuring her right knee

But this year she is happy with her form and said: "I feel like it doesn't matter what day I have, I go on the court and I feel more consistent that I can change things.

"Even if I'm not playing well, like I have always Plan B or I always can control myself. It's like I'm always there - I feel more consistent."

Elsewhere, ninth seed Daniela Hantuchova progressed by beating Vania King 6-3 7-5.

The most notable loser was Marion Bartoli, the French 10th seed, who won the first set against Sweden's Sofia Arvidsson before falling off the pace.

Bartoli was not the only casualty among the seeded women on day two.

Russia's Dinara Safina (16) lost to Germany's Sabine Lisicki in three sets.

And Hungarian hope Agnes Szavay (20) and the Czech Republic's Lucie Safarova (22) were also beaten, by Ekaterina Makarova and Catalina Castano respectively.