Abstract: By using the supermum-infimum existence theorem in set theory, the theoretical differentiation has been made for the range of floating interest rate of the loan from international business bank and of international bonds. Then, a set of new formulas had been constructed to measure the risk of international rate when a debit borrow a loan at fixed or floating rate on international financial market, thus the usual practice has been changed in risk measurement using expectation-variance criterion which also often take the capital income as a risk.