The so-called "big base" refers to the phenomenon that bank credit funds are excessively concentrated in big cities, large enterprises, large projects and certain industries. In specific work, as long as one bank is involved, other banks often compete to follow up with the big customers who have industry advantages or local economic leading enterprises, often ignoring the borrower's repayment ability and actual capital demand, resulting in "large households" and excessive credit granting, resulting in the phenomenon of customers "speculating in banks".