Thousands entered border camps and are receiving humanitarian assistance, China’s foreign ministry said.
Earlier this week, about 30 people were killed on Myanmar’s border with China after rebels launched a surprise raid.
Chinese foreign spokesman Geng Shuang said aid was being offered to those looking to “temporarily avoid the war”, and called for an immediate ceasefire, adding that China supported Myanmar’s peace process.
He said that all sides needed to find a peaceful solution through dialogue and urged restraint to “prevent further escalation” and “to restore peace and stability to the border areas”.
Five civilians, five police officers and at least 20 rebel fighters are said to have died.
Kokang has close ties to China, with locals speaking a Chinese dialect and using the yuan as currency.
The worsening conflict in the borderlands has raised tensions between Myanmar and Beijing.