China's Ministry of Finance said the government will strengthen fiscal policy, boost infrastructure spending and speed up reform of its tax system, adding to other steps to reenergize sputtering growth.
At 9:43 a.m. ET (1343 GMT), the Dow Jones industrial average was up 128.55 points, or 0.78 percent, at 16,621.23, with all 30 of its components in the black.
The S&P 500 was up 13.52 points, or 0.69 percent, at 1,982.93 and the Nasdaq Composite was up 40.73 points, or 0.85 percent, at 4,852.66.
U.S. stocks rose more than 2 percent on Tuesday, bouncing after steep losses last week.
"The fear factors regarding China and the Fed is easing somewhat and that is key," said Peter Cardillo, chief market economist at Rockwell Global Capital in New York.
"We're also seeing some of the money that was on the sidelines following the recent volatility, come back into the market."
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The Shanghai Composite closed 2.3 percent higher on Wednesday. Adding to the positive sentiment, Japan's Nikkei 225 rose 7.7 percent, its biggest one-day rise since the global financial crisis, as Prime Minister Shinzo Abe signaled a cut in corporate taxes.
All the 10 major S&P sectors were higher with the materials index's 1.37 percent rise leading the advancers.
U.S. job openings surged to 5.753 million in July from 5.323 million in June, Labor Department data showed, suggesting strength in the economy ahead of the U.S. Federal Reserve's interest rate meeting next week.
Apple shares were up 0.5 percent at $112.75. The iPhone maker is expected to unveil new offerings at its annual conference later on Wednesday.
Barnes & Noble fell 6.4 percent to $15.22 after the largest U.S. bookstore chain reported a decline in sales for the fifth consecutive quarter.
Tetraphase Pharmaceuticals sank 78.9 percent to $9.45 after its experimental bowel drug failed to meet the main goal in a late-stage study.
Dave & Buster's Entertainment jumped 9.7 percent to $41 after the restaurant and arcade chain operator raised its 2015 revenue and comparable store sales forecasts.
Advancing issues outnumbered decliners on the NYSE by 2,146 to 543. On the Nasdaq, 1,826 issues rose and 517 fell.
The S&P 500 index showed two new 52-week highs and no new lows, while the Nasdaq recorded 25 new highs and six new lows.