For the systematic evaluation of the anti-jamming performance of 5th generation advanced (5G-A) systems in complex electromagnetic environments, this study addresses the shortcomings of existing jamming test methods in simulating realistic non-orthogonal interference. A dedicated 5G-A test platform based on an orthogonal mismatch interference mechanism is designed and implemented. The platform innovatively proposes an interference generation method that destroys subcarrier orthogonality by introducing a normalized frequency offset, establishing an analytical relationship between the attacker’s frequency offset and the efficiency of interference energy diffusion. In terms of hardware implementation, the platform employs an FPGA combined with high-speed ADC/DAC modules and a configurable RF front-end, achieving precise generation and high-precision control of interference signals in terms of frequency, power, waveform, and timing. To comprehensively verify the platform’s effectiveness and evaluate the anti-jamming capability of key 5G-A channels, two test scenarios—RF cable direct connection and static/dynamic over-the-air measurement—were employed. The performance of the synchronization signal block (SSB), physical downlink control channel (PDCCH), and physical uplink control channel (PUCCH) under orthogonal mismatch interference of varying intensities was analyzed and examined. Experimental results indicate that, compared to traditional narrowband jamming, orthogonal mismatch interference can increase the terminal bit error rate by a factor of two under the same transmit power, while enabling accurate testing of the antijamming performance of the aforementioned key signals and channels. This work holds positive significance for promoting the reliable deployment of 5G-A networks.