The invention relates to a method for measuring performance parameters of an optical fiber cable circuit with ultra-long distance based on two-way testing curve fitting of dorsad scattering curves of an optical time domain reflectometer. The method comprises the steps as follows: 1) analysis memory of a one-way testing curve; 2) two-way testing curve fitting; and 3) analysis memory of the two-way testing curve. The method can greatly meet the fitting requirements of the two-way testing curve, and the analytical judgment of the two-way testing curve after fitting can be similar to analytical judgment of the one-way testing curve for the engineering technical personnel.