The September surplus with the U.S. was larger than China's overall trade surplus of $31.69 billion for the month.
For January-September, China's trade surplus with the United States was $225.79 billion, compared with about $196.01 billion in the same period last year.
China's large trade surplus with the United States has long been a sore point with Washington and is at the center of an increasing bitter dispute between the world's two biggest economies.
The United States and China imposed new tit-for-tat tariffs against each other's goods in late September, the latest escalation in a heated trade war between them.
(Reporting by Beijing Monitoring Desk; Editing by Richard Borsuk)