Study on fatigue property of asphalt mixture is very important to design rational pavement. Author gave an account of the facts about the number of cycle to failure of several asphalt mixtures in previous reports, but it seems probable that the process came to be fatigue failure is also important. So, author made the process came to be fatigue failure clear by use of the coefficient of decrease of complex modulus. From experimental results it became clear that there is a near connection between coefficient of decrease of complex modulus and strain, temperature, frequency etc.. And these relation could be easily represented by following equations. [numerical formula] where, C.D.C.M.: coefficient of decrease of complex modulus ε: strain T: temperature f: frequency a_1, a_2,～c_1, C_2: some constants