In this work the features and influences of entropy in the lytropic condensation of macromolecules were discussed. In an irregular condensation

in that the amorphous polymers were generated

just the entropy increase causes a decrease of Helmholtz’s free energy

and so that the condensation process can go on. In a regular condensation

in that the crystalline polymers were generated

the change of entropy induces very complex effects for polymer crystallization. Due to the competition between entropy and internal energy

a folded chain lamellae with loose structure was prior generated in the lytropic crystal process;and a two phases structure with crystal and amorphous region was generated in the crystal process from polymer melts. Two different change’s ways of entropy were distinguished: a jump change of entropy can induce a thermodynamic phase transition-entropy induced phase transition;but a gradual change of entropy can change only the mechanical property or initiate a mechanical state transition of polymers.