When the very fast transient overvoltage (VFTO) propagates through capacitive voltage transformers (CVT), it can create significant interference on their secondary sides, and affect the normal operation and functioning of secondary equipment. In this paper, the CVT equivalent calculation circuit model is established, and the disturbance voltage of the secondary cable is deduced and calculated. Based on the electromagnetic transient simulation software, the overall simulation model of the secondary cable disturbance caused by the VFTO in a 500 kV GIS substation is established, the interference voltage at the end of the secondary cable is simulated and analyzed, and the effects of the length of the secondary cable and the grounding mode of the shield on the disturbance are studied. It also puts forward the combined anti-interference measures of using spiral tube damping busbar, grounding at both ends of the shield, using multi-strand conductors and installing filter capacitors, which greatly reduce the amplitude and harmonic components of the disturbance voltage of the secondary cable.