He is the founder and chairman of Hillhouse Investment, the largest private equity firm operating in Asia as of October 2021.

[2][4] Lei translated Swensen's book, Pioneering Portfolio Management, An Unconventional Approach to Institutional Investment (2000), into Chinese while studying at Yale, which, according to the Financial Times, involved creating new Mandarin words for "endowment" and "fiduciary".

[5] After graduating from Yale, Lei took a role with Virginia equities firm EMM, covering Southeast Asia.

[10] In addition, Hillhouse closed the Real Assets Opportunities Fund (RAOF) with over $2 billion, with support of $300 million from CPPIB.

[11] Lei is a founding board member of the United World College (UWC) of Southeast Asia Foundation.

[22] Lei started Hillhouse Academy in association with Renmin University to prepare students in business for the technological revolution.