Abstract: A low-frequency E-field generator based on transmission line structure is designed for radio frequency susceptibility testing, which can address the challenges of large volume, low efficiency, and hard to generate high field strengths at low frequencies. A balun transformer with 1 ∶ 9 impedance transformation ratio is designed to realize the conversion of unbalanced input to balanced output, and the impedance matching between the input port and the load. The transmission line portion of the E-field generator is U-shaped conductive arms, which can produce uniform E-field distribution between the two arms. The experimental results demonstrate that the E-field generator can withstand 2 000 W continuous waves. The voltage standing wave ratio (VSWR) is less than 1.8 under small signal conditions, and does not exceed 2.0 under high-power input. The generated field strength can achieve 150 Ⅴ/m in the frequency band of 10 kHz~100 MHz, and even more than 250 Ⅴ/m in the frequency band of 10 kHz~30 MHz. It can satisfy the requirements of most electromagnetic radiation susceptibility testing standards.