The experiments on the geometric bending stiffness of 36galfan cables and stainless steel cables were carried out by frequency method. The natural vibration frequencies of three different diameters galfan cables and stainless steel cables under the three different prestress levels were measured. Then based on Bernoulli Euler theory, an iterative solution method of geometric bending stiffness was proposed. The geometric bending stiffness of three different diameters galfan cables and stainless steel cables were identified and calculated. The results show that the ratio of the geometric bending stiffness to the total section bending stiffness decrease as the diameter of the cable increases. The function relationship between the ratio and diameter is obtained.