S-fund is a fund product in the field of private equity, which specializes in obtaining fund shares, investment portfolios or investment commitments of alternative assets from investors. In the field of private equity investment, sub-fund is a kind of fund product that specially buys fund shares, investment portfolios or investment commitments of alternative assets from investors. American funds originated from American capital market, and developed rapidly since the beginning of 2 1 century, but developed slowly in China.