This study investigated the mechanical properties as well as electrical resistivity and piezoresistivity of the polyethylene terephthalate (PET)–graphite composite. The effects of graphite content, loading type, and loading rate on the performance of PET–graphite composite were investigated. Test results showed that the compressive and flexural strengths of the composite decreased rapidly as the graphite content was beyond 12 %. The electrical resistivity of the composite decreased from 3.5 × 10⁸ Ω · cm to 2.2 × 10³ Ω · cm as the graphite contents increased from 8 % to 12 %. The graphite content for the conductive percolation threshold of the PET–graphite composite was determined to be 13 %. The PET–graphite composite was sensitive to low compressive stress. When the compressive stress reached 0.7 MPa, the fractional change in the resistivity could reach 10.5 %. The piezoresistivity of the PET–graphite composite was significantly influenced by the loading rates. The field test indicated that the composite was able to detect the traffic effectively.