The authors designed a randomised overlapping ring metallic mesh and built its evaluation model of electromagnetic interference shielding effectiveness. They simulated and analysed the effects of diameter 2R and period g on electromagnetic shielding effectiveness. The simulation and experiment results show that the electromagnetic shielding effectiveness is better than 23 dB in the 10–18 GHz band while its maximum normalised high-order diffraction optical energy is decreased to 0.00134%. The randomised overlapping ring mesh can realise strong shielding effectiveness and low image-degradation simultaneously.