PURPOSE : A method for constructing and managing a web site for a real estate, a loan, a bond related service through an Internet electronic commercial transaction is provided to activate a real estate trading and a real estate security lending and to trade a bond borrowed to a buyer/construction company by connecting a real estate, a construction company, and a financial company at an on-line through an Internet electronic commercial transaction, thereby promoting an information interchange therebetween.CONSTITUTION : A construction company(S100) requests a lending to a financial company(S200) through a web server(S400). The financial company(S200) informs a lending approval to the construction company(S100) through the web server(S400) and supplies loaned money to the construction company(S100). If a buyer(S300) requests a lending to the financial company(S200) through the web server(S400), the financial company(S200) informs a lending approval to the buyer(S300) through the web server(S400). If the buyer(S300) requests for sale to the construction company(S100) through the web server(S400), the construction company(S100) informs the sale through the web server(S400). The financial company(S200) which lent a loan to the construction company(S100)/buyer(S300) taking a real estate as security requests an issuing sale of an MBS(Mortgage-Backed Securities) to a flowing agency(S500) for promoting a revulsion of a real estate security lending. The flowing agency(S500) pays an MBS selling price for a general investor(S600) to the financial company(S200).? KIPO 2002