Piezoelectric fiber composite is an emerging smart material and exhibits much broader applications than traditional piezoelectric ceramics, especially in light-weight and curved structures. Piezoelectric fiber composites with different fiber thickness and volume fraction were fabricated. The effects of structural parameters, i.e. different fiber thickness and volume fraction, on the strain properties and actuation performance of piezoelectric fiber composites were investigated at different excitation voltages at frequency of 0.1 Hz. The results indicated that the free strain and tip displacement decreased with the increasing thickness of piezoelectric fiber. When 1000 V voltage was applied, the free strain and tip displacement for the composite with fiber thickness of 200 mu m were 665 mu epsilon and 1.9 mm, respectively, which were much higher than those of composite with fiber thickness of 300 mu m or 400 mu m. Piezoelectric fiber composites exhibited orthotropic actuation properties, and higher free strains with larger fiber volume fraction. The longitudinal and transverse free strains of composites with 74% fiber volume fraction were 2.04 and 1.72 times magnitudes of composites with 59% fiber volume fraction, respectively. The transverse effect coefficient, the ratio between transverse and longitudinal free strains, decreased from 0.519 to 0.451 when the fiber volume fraction decreased from 74% to 59%.