According to a new survey by the global market research firm International Data Corp, smartphone shipments in China fell 4.3 percent in the first quarter compared with a year ago for the first time in six years.
The slowdown is largely driven by the disappearance of China's first-time buyers, the survey said.
In the first quarter, Apple became China's largest smartphone maker by market share, surpassing Xiaomi on the strength of its popular iPhone 6 and iPhone 6 Plus.
Samsung has fallen to fourth place in China in the first quarter, from the top spot a year ago. Coolpad Group Ltd. was China's No. 5 smartphone maker last year on the strength of budget phones but fell out of the top five in the first quarter, according to IDC.
According to Tom Kang, research director with market-research firm Counterpoint, "China is now a replacement market".
The slowdown has major implications not only for Apple and Samsung as well as China's homegrown phone makers like Xiaomi Corp.
"The smartphone market in China is basically now just the very high end like Apple or the very low end. It is getting tough for those in the middle," Charles Lin, chief financial officer of Pegatron Corp which manufactures smartphones for Apple and some Chinese brands, was quoted as saying.
Xiaomi, started five years ago, is now valued at $46 billion. Last week, it unveiled Note Pro, a phone about the size of the iPhone 6 Plus and costing about $480.
"We will keep pursuing our mission to make high-quality, high-performance phones at affordable prices for our customers," a Xiaomi spokeswoman was quoted as saying in the report.
"While there are signs that the explosive growth of smartphones in China will slow this year, the vast majority of China's 885 million mobile users are using low-end and mid-range smartphones," Samsung said in a statement.
"This leaves plenty of room for upgrades to high-end phones as China's market matures," it added.