The rise beat the poll's forecast for a 15% gain.
China has been credited with helping to support global demand and weaker imports might hurt suppliers for whom this country is a major market.
Trade figures in dollars will be released later in the day.
Trade surplus shrank 17.7 percent to 2.03 trillion yuan in the same period.
He cited favorable factors for trade growth including mild recovery in the world economy, strong economic momentum inside China and good prospects for trade with other emerging markets.
China's imports from North Korea fell for a seventh straight month in September, dropping 37.9% year-on-year as Beijing implemented the latest United Nations trade sanctions aimed at persuading Pyongyang to rein in its nuclear and missile programmes.
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Exports increased 12.4 percent to 11.16 trillion yuan, while imports surged 22.3 percent to 9.13 trillion yuan, the General Administration of Customs (GAC) said. Imports rose 18.7%, exceeding estimates with the fastest growth since March, to result in a trade surplus of $28.5 billion. The surplus grew to $28.08 billion from $26.23 billion in August.
China's September iron ore imports rose to a record 103-million tonnes, up from 88.7-million tonnes in August, according to Reuters calculations.
China-US ties have been strained by President Donald Trump's criticism of China's trade practices and by demands that Beijing do more to put pressure on North Korea.
With the European Union, China's exports rose 10.4 percent and imports 30.9 percent.
China is also in the midst of its toughest environmental crackdown ever, ordering many mills, chemical plants and coal companies to sharply reduce output or close in coming months to reduce the country's notoriously thick winter smog.