To address the structural reliability issues caused by the deflection deformation in the crimping zone of 300/40 carbon fiber core or rod-core conductors， a deflection calculation method based on the Timoshenko beam theory is proposed. A deflection formula of the crimping zone is derived theoretically with the consideration of the shear effect， which is validated subsequently through finite element simulations. The results show that under a 10 t crimping load， the maximum deflection of the crimping zone of the 300/40 carbon fiber core conductor with a length-to-diameter ratio of 17.14 is 0.011 6 m， which matches well with the finite element simulation result， i.e.， 0.012 8 m. The theoretical solution with a simple form can offer a high calculation accuracy. It can avoid the complex modeling and meshing processes involved in finite element analysis， significantly improving computational efficiency and offering good applicability. It is also suitable for the deflection calculation for the crimping zone of 300/50 steel-core aluminum stranded conductors. The research results can provide an important reference for optimizing the crimping process and engineering applications of carbon fiber composite core conductors.