No nonstop from Daxing. Dulles is the Washington airport with China service, but the Beijing end of it is Capital, not Daxing.
There is no nonstop PKX–IAD flight
Beijing Daxing carries no scheduled service to Washington Dulles International Airport. This is not a seasonal gap: when Daxing opened in 2019 it took the domestic network and a limited set of international routes, while Beijing’s transpacific long-haul stayed at Beijing Capital (PEK).
Two things follow. First, a ticket that says “Beijing” is not self-explanatory — check whether it means PKX or PEK before you plan anything around it. Second, if your itinerary genuinely starts at Daxing, you are looking at a connection: either through another Chinese hub, or a change of airport in Beijing, which is a two-hour journey across the city rather than a connection.
Daxing has no North American service at all, so the change of airport is usually unavoidable. Give yourself a clear margin: the road transfer between the two Beijing airports takes about two hours in normal traffic, and it is not covered by a single ticket unless your airline sold it that way.