This study investigates the effects of the pre-strain level on mechanical properties of the solid-phase formed thermoplastic composite. A uniaxial solid-phase forming was performed at the temperature of 125$^{C}$ and at the constant cross-head speed of 3mm/sec. The composite sheet was formed to various pre-strain levels of 10%, 20%, and 30%. Tension, flexural, and impact tests were carried out to characterize the material properties of a solid-phase formed part. Tensile and flexural strengths decreased with increasing the pre-strain level, while impact strength increased. Various microstructures of the formed part explained the above material behavior.