The IPO opened at a price of HK $16.60 (about $2.12 USD) per share which is a fair amount below the original IPO value of HK $17.
Let us know in the comments if you think Xiaomi will do well in the medium and long term in terms of its stock price.
It's also a disappointment for Hong Kong, which this year revised regulations to allow tech companies with uneven voting structures like Xiaomi to float.
A new wave of Chinese tech companies are planning forays into public markets to raise billions of dollars through initial public offerings.
Xiaomi's float was the first under the city's new rules allowing firms to weight voting rights in favor of company founders, as part of efforts to encourage more tech groups to choose Hong Kong over NY, its arch-rival. But in a surprise move last month, it postponed its mainland share offering.
Typically companies are valued on a multiple of profits or sales.
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The company, which makes phones to rival Apple's iPhone, had hoped to hit a valuation of $100bn in the float, but is now valued at around $53bn. The main Hong Kong stock market index ended 1.3 percent higher.
The float adds to Hong Kong's $7 billion worth of new listings this year.
"We are an internet firm". It is also the first under the city's new rules permitting dual-class shares, common among US tech firms, in an attempt to attract tech sector floats.
By contrast, China Literature Ltd, the e-book arm of Chinese gaming and social media firm Tencent Holdings, late a year ago raised US$1.1 billion for its Hong Kong IPO amid heavy demand, with the retail portion being 625 times oversubscribed.
But doubts about the sustainability of its business model were among the reasons for the lower valuation, analysts said.
It is now the biggest smartphone vendor in India and is pushing into European markets including Spain and Russian Federation, though it has lost share in China recently to lower-cost rivals.