The ethyl-cyanoethyl cellulose [(E-CE)C]/poly (acrylic acid) [PAA] composites were prepared via in situ photopolymerization of the (E-CE)C/acrylic acid (AA) solutions, in which the morphology and structure of (E-CE)C was retained as the same as that in the solution. The strength and the modulus of the composites depended on their morphology and structure. The strength of the composites with a completely amorphous state or with a completely cholesteric order did not significantly change with increasing (E-CE)C content, although the strength of the composites with completely cholesteric order is much higher than with the completely amorphous state. However, when the (E-CE)C content changed from 33.8% to 42.5%, in which the composites had both cholesteric order and amorphous phases, the strength of the composites greatly increased with increasing (E-CE)C. The elastic modulus of the composites with completely isotropic structure decreases with increasing (E-CE)C content but abruptly increases with increasing the fraction of cholesteric phase in the composites. The (E-CE)C with cholesteric order had a significant enhancing effect on the strength of the composites. The stress-strain curves indicated that the composites with completely amorphous or completely cholesteric order were breakable, while they were tough in the case when they had both cholesteric and amorphous phases.