United Airlines flies San Francisco to Beijing nonstop with $478 round trip tickets for the next three weeks. Prices rise in mid-December and most of January-February before dropping to $498 February 17 through April 29.
United Airlines San Francisco – Beijing PEK nonstop
An alternative is Air China nonstop flights SFO-PEK, another Star Alliance member. Air China Economy L class earns 25% flight miles in United Mileage Plus or even 100% flight miles in Avianca. Miles & More members earn 50% with Air China L. SFO-PEK-SFO = 11,826 flight miles.
Air China San Francisco SFO – Beijing PEK nonstop