China has admitted its state-run weapons manufacturers held talks in July with representatives of Colonel Gaddafi as his forces battled rebels.
A spokeswoman said the meetings in Beijing took place without the knowledge of the government.
She said that no contracts were signed and no arms supplied.
The UN Security Council passed an arms embargo on Libya in February as anti-Gaddafi protests gathered pace.
The Chinese response followed a Canadian newspaper report that said three state-run Chinese firms had offered up to $200m (£124m) in weapons to Col Gaddafi's envoys when they visited from 16 July.
Citing documents found among rubbish in a part of Tripoli home to many of Col Gaddafi's former senior officials, the Toronto-based Globe and Mail said the weapons on offer included anti-tank missiles and rocket launchers.
The documents said the companies suggested shipping the arms via Algeria or South Africa, but did not confirm whether any military assistance was delivered, the newspaper reported.
Chinese foreign ministry spokeswoman Jiang Yu told a daily press briefing that no arms had been sent.
"The Gaddafi government sent personnel to China without the knowledge of the Chinese government and who engaged in contact with a handful of people from the companies concerned," she said.
"The Chinese companies did not sign arms trade contracts and nor did they export military items to Libya."
Domestic agencies in charge of weapons' trading "will certainly treat this seriously", she added.
The admission will complicate China's relationship with Libya's incoming regime, says the BBC's Damian Grammaticas in Beijing.
China still has not recognised the rebels as Libya's new government and the new admission seems to confirm that while Col Gaddafi's rule was nearing its end China was continuing to hedge its bets.
In June China had hosted Libya's rebel leadership in Beijing as it sought to build contacts with them. Now it is clear that just a few weeks later Col Gaddafi's men were seeking weapons from China.
Libya's new leaders may find it hard to believe that China did not know that Libyan officials were in the country trying to secure such a large order of weapons from Chinese state-controlled firms, our correspondent adds.
And there have already been suggestions that China's lack of support for the rebels may mean its companies lose out on future deals for Libya's sought-after oil supplies.