To address the electromagnetic pulse protection requirements of the RF front-end in a complex electromagnetic environment, a strong electromagnetic pulse protection circuit working in the L-band is designed. This circuit uses PIN diode as the core device, adopts a multi-level PIN diode cascaded protection structure, connects each stage through microstrip transmission lines, and optimizes the design. The performance of the circuit under different working conditions is verified by simulation, and its physical test is carried out. The test results show that in the L-band, its insertion loss is less than 0.6 dB, the return loss is more than 11.93 dB, and the standing wave ratio is less than 1.68, indicating good signal transmission performance. Under the injection of a 4 kV square wave pulse, the circuit can respond quickly within 1 ns, and the peak leakage voltage generated by the circuit is 69.636 V. After 2 ns, the stable output voltage of the circuit is less than 20 V, indicating that the circuit has good transient protection capability against fast-edge pulse. Combined with the low-loss characteristics in L-band, the circuit can provide effective electromagnetic pulse protection support for equipment working in L-band.