The human rights organisation Amnesty International has accused China of being one of the world's most secretive and irresponsible arms exporters.
China is an increasingly important arms producer
It says Chinese weapons helped fuel conflicts in Sudan, Burma and Nepal.
Amnesty urged China to stop exports that could be used for human rights violations, and to publish information on its arms exports.
China rejected the accusations, insisting it had strict safeguards to prevent any unethical sales of weapons.
Amnesty challenged these safeguards in its report.
"China describes its approach to arms export licensing as 'cautious and responsible', yet the reality couldn't be further from the truth," the author's report, Helen Hughes, said in a statement.
We're calling for China to enact commitments banning all arms transfers where they are likely to be used for human rights violations
"China is the only major arms exporting power that has not signed up to any multilateral agreements with criteria to prevent arms exports likely to be used for serious human rights violations."
The report alleges that in 2005, Beijing shipped 200 Chinese military trucks to Sudan and that it is supplying the ruling military junta in Burma with weapons.
China rarely comments on its arms exports, though it is one of the junta's few firm allies.
The report also accuses China of selling rifles and grenades to Nepal's security forces at a time when there was a mass uprising against the monarchy by civilians.
The report says China exports more than $1bn worth of weapons a year, often exchanging arms for raw materials needed to fuel its economy.
Amnesty urges China to change its current practices to be more transparent and to support the international initiative for an arms trade treaty.
"We're calling for China to enact into law and uphold commitments... banning all arms transfers where they are likely to be used for human rights violations," Ms Hughes said.
China has long said it had a careful approach to weapons sales, only issuing licences after examining each application individually.
The focus on its arms exports comes amid US concerns that China's military spending is growing much more quickly than it officially acknowledges.
China has also been actively campaigning the European Union to lift its ban on weapons sales to China, imposed following the 1989 Tiananmen Square massacre.