The net asset value of Yu'e Bao stood at 972.4 billion yuan ($149.92 billion) at end of the first quarter, according to the fund's Q1 report on Thursday, down 18.3% from that of 1.19 trillion yuan at end of 2020.

The drop came as regulatory pressure mounted on Jack Ma's Ant Group.

China has imposed a sweeping restructuring on Ant Group, the fintech conglomerate whose record $37 billion IPO was derailed by regulators in November, underscoring Beijing's determination to rein in its internet giants.

The overhaul, directed by China's central bank, subjects Ant to tougher regulatory oversight and capital requirements, and requires it to cut links between its hugely popular payments app Alipay and its other businesses.

The Chinese regulators' decision to require the delinking of Ant Group's microlending business from Alipay is further evidence of the authorities' focus on reducing risks to financial system and social stability posed by the online microlending sector, as well as efforts to rectify anti-competitive behaviour in the third-party payments market, Fitch Ratings said in a report.

Gains in the equities market could also have played a role in the decrease, as China's blue-chip index hit an all-time high in mid-February, dampening the appeal of money market funds and prompting more retail investors in Yu'e Bao to put money in mutual funds that invest in stocks.

Ant Group is the payment affiliate of Alibaba Group Holding Ltd.

Set up in 2013, Yu'e Bao is targeted at individual investors and now one of the biggest money market funds in the world, and is integrated with Ant Group's Alipay.

(Reporting by Luoyan Liu and Andrew Galbraith; editing by David Evans)