In the present paper, the conclusion we arrive through analyzing the (dTc/dλ)-λ curve is that the Tc-λ curve is composed of three parts with entirely different properties, namely, "McMillan region", "λn region" and "series solution region". This conclusion is identical with that obtained in paper [20] except that the value of n is, in general, not equal to 1.55 but is a real number larger than 0.5 and varies with, the shape of the effective phonon spectrum.