The effects of the annealing process on the mechanical properties and crystallization behaviors of polypropylene random copolymer (PP-R) composites were investigated using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The experimental results indicated that the annealing process significantly influenced the comprehensive properties of PP-R composites. At temperatures below 23 ℃, the impact strength of the PP-R composites annealed at 120 ℃ for 6 h was relatively high at 74.73 k J/m2, which was 16.8％ higher than that of the samples annealed at 80 ℃ for 6 h. At low temperatures (-30-0 ℃), the impact strength ranged from approximately 13.31 k J/m2 to 54.4 k J/m2. In addition, the annealing process conducted at 120 ℃ for 6 h improved the crystalline structure and low-temperature toughness of the PP-R composites and induced α-form to β-form crystal transformation. The work provides a possible method to reinforce and toughen the semicrystalline polymer at low temperatures (-30-0 ℃) by annealing.