The Socialist candidate for the French presidency, Segolene Royal, has begun a three-day visit to China.
Ms Royal visited the Great Wall of China
She is expected to discuss environment, trade and human rights issues with Communist Party leaders in Beijing.
At the start of her trip, Ms Royal urged French business to see China's economic rise as an opportunity.
Correspondents say the visit is a chance for Ms Royal to address criticism that she lacks experience in foreign affairs.
The BBC's Hugh Schofield in Paris says China poses a particular diplomatic challenge, as many on the French left regard its economy as a threat and its record on human rights and the environment as deplorable.
While Ms Royal cannot ignore these concerns, our correspondent says, she will also have to assure her hosts she will maintain the strong partnership pioneered by the current President, Jacques Chirac.
Ms Royal was shown on French TV visiting the Great Wall of China, after arriving from Paris on an overnight flight.
"China is a huge market for French companies that demonstrate perseverance, creativity, will," she told reporters during the tours.
She also visited a construction site for the 2008 Olympics, where she urged French companies not to be afraid of the Chinese market.
"If companies organise themselves better, if they work together to export, then we will not only protect our economy but also create jobs in France," she said.
Speaking before her trip, Ms Royal said she planned to discuss human rights with her hosts but did not intend to preach.
"I am not going as a giver of lessons," she said.
Opinion polls give Ms Royal a narrow lead over her rival, Interior Minister Nicholas Sarkozy.
Ms Sarkozy recently attacked Ms Royal for meeting a lawmaker from the militant Hezbollah group on her first foreign trip, to Lebanon.
France's presidential elections are due to be held in April.