Delta is offering the low fare of $767 round-trip from BWI (Baltimore-Washington) to Beijing. This fare is available for quite a few date pairs in March and April, a good time to go before the summer heat builds in Beijing. Note that it’s in Premium Economy, with the extra legroom that you will cherish for this long flight.
Secret Flying has the details and some date pairs.
If you want to stop over in Baltimore-Washington, there is plenty to see and do in both cities.