CSRC officials did not respond to requests for comment.
Xiaomi was set up in 2010 and doubled its smartphone shipments in 2017 to become the worlds fourth-largest maker, according to Counterpoint Research, defying a global slowdown in smartphone sales.
Its listing has come at a delicate time for China's stock markets, with the CSI 300 index of the country's top blue-chips falling 4.3 per cent this month and 10.9 per cent this year amid fears of a trade war with the United States.
"The China stock market is so fragile," said David Dai, general manager of Shanghai Wisdom Investment Co Ltd, a hedge fund. "I think Xiaomi is worried about its valuation and is considering a China listing at a better time." The government needed to stabilise the market if it wanted to preserve its ability to raise capital for companies, he added.