"It's really simple: Baidu's top-line growth accelerated year over year," said Susquehanna Financial analyst C. Ming Zhao.
Baidu shares have returned to record levels hit in the middle of this month before worries about the U.S. economy dragged down stocks. It is up 127% in the last three months.
In extended trade, shares traded at $218, after closing at $183.23 on Nasdaq before the results were released.
Baidu posted a second-quarter profit of $18.6 million (141.9 million yuan), or 54 cents a diluted share.
Those figures compare to the year-ago quarter's net profit of $7.3 million (58.5 million yuan), or 21 cents a share.
Excluding one-time items and stock option expenses, it reported 57 cents per diluted share, beating analysts' average forecast for 50 cents a share, according to Reuters Estimates.
Revenue rose 109% to $52.7 million (401.3 million yuan), exceeding an average forecast of $48.4 million, according to Reuters Estimates.
For the third quarter, Baidu said it expected no slowdown in its rate of growth, projecting revenue in a range from $64.6 million to $66.5 million (492 million to 506 million yuan), which translates into growth of 106% to 111%.
The number of Baidu's active online marketing customers during the second quarter grew to around 128,000, an increase of 14.3% from the first quarter and 42% from a year ago.
Baidu dominated the search market in China in the second quarter with a 58.1% share, followed by Google with 22.8% and Yahoo China with 11.6%, research firm Analysys International reported.
With over 162 million Web users, China is the world's second-largest Internet market after the United States.
Baidu has been gobbling up market share mainly from smaller operators and Yahoo. It also overtook major portal SINA early this year as the largest Web advertising supplier in China, according to a recent report by broker research firm CLSA.
Earlier this year, Baidu introduced a Japanese-language version of its Web search service in Japan, its first bid to expand outside of China.