Abstract: Based on Channel and Components Requirements for 1000BASE-T1 Link Segment Type A (STP) formulated by TC9 Technical Committee of one-pair Ethernet (OPEN) Alliance, key technologies for domestic production of high-speed Ethernet harnesses for new energy vehicles were studied, and test methods for transmission performance and electromagnetic compatibility, including parameter tests such as characteristic impedance, insertion loss, and return loss, as well as shielding performance evaluation by three-axis tube method were emphasized. Comparing performance data of domestic and imported harnesses, it was found that domestic harnesses had approached international standards in basic transmission performance (such as characteristic impedance, propagation delay, and insertion loss), but there was still a gap in terms of high-frequency signal integrity and anti-interference capabilities. Specifically, margins of longitudinal conversion loss and longitudinal conversion transfer loss were low, and anti-common-mode interference capability was insufficient; external crosstalk attenuation performance was weak, and multi-bundle interference suppression capability needed to be improved; coupling attenuation and shielding attenuation were not up to the standards in high-frequency band (30~600 MHz), especially above 500 MHz there was significant gap with imported products. Further analysis indicated that these gaps mainly resulted from insufficient shielding structure processing, such as large weaving angles, aluminum-plastic tape winding methods, and connector pressing accuracy. To achieve breakthroughs in domestic production, research efforts should be strengthened in the following aspects: firstly, optimize high-frequency shielding processes by adopting small-angle weaving and longitudinal aluminum-plastic tape structures; secondly, improve precision assembly technology of connectors and cables to reduce signal leakage.