The Chinese star reached the last 32 with a comfortable 6-0, 6-2 win over France's Stephanie Foretz Gacon despite a potentially hostile crowd on Suzanne Lenglen court.
"I was a little bit nervous at the beginning. It's always tough against a French player in Paris - I saw the match two days ago, so I was a little bit nervous," said Li.
She was referring to Williams' sensational defeat to French outsider Virginie Razzano on Tuesday, the American's first opening round defeat in her Grand Slam exit.
Li, 30, the seventh seed and Asia's first and only Grand Slam singles winner, immediately took the French supporters out of the match by breaking Foretz Gacon in the first game with aggressive baseline play.
And there was no sign of any nerves on her part after the first game.
If anything, it was the Frenchwoman, ranked 86th in the world, who was overcome by the jitters and handed Li her second break with a double fault.
Li, who had never lost before the third round in any of her previous five appearances at the French Open, scored the third break with a backhand crosscourt winner before comfortably serving out the first set.
The 31-year-old Foretz Gacon, making her 14th consecutive appearance at Roland Garros, avoided total humiliation by breaking Li halfway into the second set but the Chinese star held firm and closed out the match when her opponent hit a long return.
It was all over in 52 minutes.
Asked if she enjoyed being the defending champion, Li said: "I really don't think too much about being defending champion and how far I can go."
"I just enjoy playing everyday."
Li, who became the fifth oldest first-time Grand Slam champion in the Open era when she won last year, said she considers the upcoming London Olympics as important as the French Open.
"I think this is my last time to play the Olympics," she confided. "You never know what happens after four years."
Li was part of the Chinese team in Sydney 2000 and and Beijing 2008, where she placed fourth.
She will have an American opponent in the last 32 at Roland Garros with Christina McHale due to face compatriot Lauren Davis later in the day.
Her Chinese comptriot Peng Shuai, the world number 30, will face Lourdes Dominguez Lino of Spain for a place in the final 32.
In the other Asian singles match of the day, Japan's Ayumi Morita will have the daunting task of taking on Russian second seed Maria Sharapova, who is seeking to lift the only major trophy she has never won.
Fear of Serena shock drives Li Na into third round
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