"Smartphones are becoming increasingly saturated in China,” said Kitty Fok, Managing Director at IDC China. “China is oftentimes thought of as an emerging market but the reality is that the vast majority of phones sold in China today are smartphones, similar to other mature markets like the US, UK, Australia, and Japan. Just like these markets, convincing existing users as well as feature phone users to upgrade to new smartphones will now be the key to further growth in the China market.”

Apple was the top smartphone vendor in China in the first quarter of 2015, with consumers still having a strong appetite for the larger screens on the iPhone 6 and iPhone 6 Plus. Xiaomi slipped to the second position as it faced strong competition from other vendors in the low to mid-range segment of the market, while Huawei maintained third position as it saw a good uptake in the mid-range segment. Samsung and Lenovo both led the market at least once last year, but rankings have since changed quickly, highlighting the volatility of consumers' brand preference in China.

IDC expects relatively flat growth for China in 2015.

"To successfully combat local players overseas, Chinese vendors will need to focus on channel relationships and localized marketing strategies," said Tay Xiaohan, Senior Market Analyst with IDC Asia/Pacific's Client Devices team. “Most of the market’s growth will come from sub-US$150 phones as feature phone users switch to low-cost smartphones."