Textile reinforced polymer composites have excellent structural performance including mechanical properties and thermal properties, which are benefited from their relative complex architecture of the reinforcement. Tailoring the geometry of the fabric can achieve desired material properties, but the complex geometry imposes some challenges to explore such a design space. The present study intends to develop a design optimization method for enhancing the thermal conductivity of plain woven textile composites. Parametric formulations for both the architecture of the reinforcement and the effective thermal properties, which are predicted by using an analytical homogenization method, are derived. Based on these explicit formulations, the sensitivities of thermal conductivities of the textile composites with respect to the geometric parameters for the reinforcement can also be derived, and the thermal conductivity optimization problem is numerically solved by using the gradient-based method. Numerical examples are presented to illustrate the effectiveness of the proposed method, where a carbon fibre reinforced plain woven textile composite is considered for the illustration purpose. Results show that the proposed approach can provide efficient solutions in terms of the enhancement of thermal performance.