The deal is the latest in a string of overseas investments for China's biggest chemical company, also known as ChemChina, as Beijing prods its companies to "go out" to expand.
Syngenta's board recommended the offer of $465 a share, plus a special dividend, to its shareholders, saying in a statement that "the proposed transaction respects the interests of all stakeholders".
The statement said the deal "will enable further expansion of Syngenta's presence in emerging markets and notably in China".
The Swiss company reportedly rejected a higher USD 47 billion bid from rival Monsanto in August last year, and the US agribusiness giant could come back with a counter-offer.
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The transaction is also likely to face regulatory hurdles -- much of Syngenta's business is in the US, where a USD 18.5 billion offer by Chinese state-owned energy company CNOOC for American rival Unocal failed in 2005 in the face of political pressure.
An analyst at Germany's Baader Bank said prior to the announcement that a deal would be welcomed by investors given the size, however, "it could pose political problems."
It is also bigger than China Unicom Hong Kong Ltd's purchase of China Netcom Group Corp for USD 28 billion in 2008, according to data from Bloomberg.
The Chinese government has encouraged its companies to invest abroad to secure raw materials and markets, while growth is slowing at home.
The deal is the latest in a string of acquisitions by ChemChina, which last month bought a 12 percent stake in Swiss energy and commodities trader Mercuria to expand its portfolio.
Last year it announced the takeover of Italian tyre maker Pirelli, renowned for its Formula One equipment and racy calendars, in a deal valued at 7.4 billion euros.
Syngenta said its existing management will continue to run the company, which will remain headquartered in Switzerland.