Midfielder Carli Lloyd had a scoring opportunity in the 20th minute but sent a hard-hit ball sailing over the net.
Less than a minute later, the Delran native had another scoring chance, but her shot deflected off a Chinese defender, just missing the left goal-post.
"I don't know how the defender deflected that one. I saw it going right in," Lloyd said.
After a clear of a U.S. corner kick, the Chinese took the ball down the left side of the field. Zhang Rui sent a low shot to the back of the net to give the Chinese the lead, 1-0, in the 22d minute.
"Sometimes it just takes a little time to get the feel of the game," U.S. goalkeeper Hope Solo said.
"Each game provides something different for us. We played China last week, and I think they knew what to expect and they changed their game plan, so we had to figure out how to change it back.
"It just takes time."
Morgan scored the equalizer from 10 yards out in the 34th minute.
Midfielder Heather O'Reilly, from East Brunswick, N.J., played the initial shot into the box and Morgan found the rebound with a perfectly placed shot.
Two minutes later, the Americans took the lead when Shannon Boxx headed the ball high inside the 6-yard line and a Chinese defender hit it into her own net. Neither team struck again in the first half, keeping the score 2-1 at halftime.
Christie Rampone, the team captain from Point Pleasant, N.J., sent a long ball to Morgan in the 50th minute. Morgan chased it down, outpacing her defender before knocking the ball into the bottom portion of the net. The goal put the Americans up, 3-1.
Abby Wambach added a fourth goal for the American side in the 83d minute when she took a throw-in from Morgan and hit the ball high and over the goalkeeper's head.
One of four games before the Olympics, the match was just one of two being held in the United States. It was also the team's first official game since April 3.
The team will play its last game in the States on June 30 in Utah, when it faces Canada.
Earlier Sunday, Sundhage announced the final roster for the Olympic team. Lloyd, O'Reilly, and Rampone earned spots on the squad, as did Basking Ridge, N.J., native Tobin Heath and Nicole Barnhart of Gilbertsville, Montgomery County.
The London Games will be the fourth for Rampone, a U.S. record, while O'Reilly and Lloyd will be appearing in their third and second games, respectively.
"Performances like this, being able to play in front of a sellout crowd, it is awesome," Wambach said. "It is kind of funny, because when I first got on this team, I was totally spoiled. We were playing in front of crowds like this when Mia [Hamm] was on the team and we took a little bit of a lull in the mid-2000s. Now we are back on top."