Abstract: On the basis of our previous work it has been found that the 1/ƒ noise is a kind of "phase" with a developing process.And the fact that the 1/f noise can be finally formed or not depends on if the minimum demand for reliability of M^#>500 being satisfied.Moreover this is also a criterion for distin-guishing 1/ƒ noise.Subsequently it can be learnt that the entropy of 1/f noise is S^*=A×10-20erg/k and S^* is a minimum value for all kinds of 1/ƒ noise,which is their general character.But,for different 1/f noise A is a variable value,which represents the individual character of 1/ƒ noise.