Abstract: DC-link capacitors are widely used in flexible DC transmission systems. The core component of these capacitors is made by winding dielectric films, which generates inter-layer pressure during the winding process. The inter-layer pressure has a significant impact on the insulation performance of capacitors, however, its measurement and calculation pose challenges and lack consensus within the industry. In this paper, based on the current calculation model of inter-layer pressure inside the circular element, the internal pressure of the element with 2 layers of coarse film and 2 layers of metallized film was measured several times by using a semi-automatic winding machine. The measured results show that the dispersion of the measured data is small and the reproducibility meets the requirements. However, the measured inter-layer pressures inside the elements are more than one order of magnitude stronger than the current theoretical calculation pressure. Through research and analysis, it is proposed that the current calculation model of interlayer pressure of circular element does not consider the influence of traction force of winding machine on the interlayer pressure, nor does it consider the influence of the change of winding diameter on the inter-layer pressure. Based on the principle of torque balance, this paper proposes an improved computational model for interlayer pressure. Additionally, incorporating experimental data, a correction factor is introduced into the computational model to account for the traction force applied during the winding process. The research provides a method for measuring the distribution of interlayer pressure between dielectric films within cylindrical capacitor components and presents a refined theoretical calculation approach. These findings offer valuable guidance and recommendations for optimizing capacitor winding processes.