Spillovers of the end of the U.S. Federal Reserve's quantitative easing (QE) stimulus program are set to add difficulties to the Chinese economy, which has seen substantial downward pressure this year, economists have warned.

The Fed said overnight on Wednesday that it had decided to end its monthly asset-purchase program, as it "continues to see sufficient underlying strength in the broader economy to support ongoing progress toward maximum employment in a context of price stability."

HSBC chief China economist Qu Hongbin shared on Sina Weibo, the Chinese equivalent of Twitter, that the Fed's decision marked an end to the 6-year-old policy, launched during the financial crisis in 2008.

QE, despite its faults, has helped the U.S. economy recover gradually. In comparison, the Eurozone economy is facing a second downturn, Japan's recovery seems to be short-lived and the Chinese economy is preparing for downward pressure, Qu said.

The U.S. dollar index rose by around 1 percent following the QE announcement. A strong U.S. dollar is likely to result in the appreciation of the Renminbi against other currencies, which is set to put more pressure on China's slowing economy, he said.

China's economy, the second largest in the world, slowed to 7.3 percent in the third quarter of 2014, the slowest quarterly growth since 2009/Q1.

Guan Qingyou, senior analyst at Minsheng Securities, predicts a strong U.S. dollar in the medium and long term; bearish gold market; and continuously sluggish commodity prices following the end of QE.

China's yuan funds outstanding for foreign exchange are expected to continue dropping, which will force the People's Bank of China (PBoC), the central bank, to change money supply channels, Guan said.

The PBoC is expected to continue using such monetary policy instruments as re-lending, pledged supplementary lending (PSL) and standing lending facility (SLF) next year, he said.

The PBoC has been using these instruments over the past few months to inject cash into the market and to ease liquidity.

Guan also said the end of QE will have a negative impact on the recovery of exports, and China might have to take more growth-supportive measures and expedite reforms.

The U.S. economic recovery this time comes alongside trade rebalance measures, so the U.S. recovery is not likely to push up China's exports, he said.

On the contrary, China's exports will face more pressure given the Renminbi appreciation against other currencies.

The Chinese economy will have to rely more on internally-driven growth, so more mini-stimulus measures and more reform exploration, via the free trade zone, are likely, Guan added.

Chinese President Xi Jinping on Monday said the experience gained from the Shanghai Free Trade Zone, since its launch in September last year, "should be replicated as soon as possible".

Ma Guangyuan, an independent Beijing economist, said the end of QE would mark a historical turnaround in U.S. monetary policy leading toward a solid recovery of the U.S. economy.

The impact of the end of QE on emerging markets has just begun. Two things are certain -- the flow of dollar funds from emerging markets to the U.S. and a strong U.S. dollar, Ma said.

"These will impact China," he said. "There is not much room for China to make monetary policy mistakes."

Former Fed chief economist David Stockton, however, played down the impact the exit will have on China.

The removal of the Fed's accommodation will have varied affects on different emerging-market economies.

"For China, the spillovers are likely to relatively minimal, as China has little dependence on foreign capital inflows. But for other emerging market economies, the spillovers may prove more painful," he said.

"Investors around the world should prepare for a period of heightened volatility [...] Even if the Fed is ultimately successful, there will likely be many many bumps along the path to normalization," Stockton added.