<p>Graphene-copper (Gr-Cu) composites exhibit significant potential for industrial applications. Among the methods for fabricating Gr-Cu composites, the in-situ growth method stands out as a simple yet effective approach. However, graphene converted from liquid or solid molecules by the traditional in-situ growth method often exhibits numerous defects, thereby reducing its effectiveness in enhancing the electrical properties of the composites. To address this issue, we developed an innovative and efficient method, referred to as the “confined-parallel-space in-situ growth (CPS) method,” to grow high-quality graphene and fabricate high-conductivity Gr-Cu composites. Oleic acid was chosen as the small molecular carbon source and confined between copper sheets obtained by rolling dendritic copper powder. This carbon source underwent conversion into oriented, high-quality graphene in the confined space at high temperature. The high-quality graphene sheets serve as continuous electron transport channels, significantly improving the conductivity of the composite. The composite prepared by the CPS method (CPS-composite) demonstrates unique conductivity, exceeding that of standard annealed copper at temperatures above 40&#xa0;°C and notably outperforming it by 3.2% at 160&#xa0;°C. In addition, compared to the composite with a similar carbon content prepared by the traditional in-situ growth method, the yield strength of the CPS-composite increased by 23.6%, while the strengthening efficiency of graphene improved by 146.6%, achieving an ultrahigh value of 489 at a carbon volume fraction of 0.086&#xa0;vol%. The CPS method emerges as a novel strategy for fabricating high-performance, low-cost, and large-scale graphene-copper composites using small molecular carbon sources, making it suitable for industrial production.</p> Graphical abstract <p></p>