Abstract: Aiming at the problems of high Q, narrow bandwidth, limited input power, low efficiency of antenna system, which are caused by the low radiation resistance and the high reactance of the VLF transmit antenna, this paper proposes a new idea to study the input impedance of VLF transmit antenna under the different loaded electrical connection without changing the overall structure. The calculation results and theoretical analysis indicate that optimized top load connection can decrease the input impedance of the VLF transmit antenna, improve the input resistance of the antenna, thus improve the efficiency and power capacity of the antenna system, and increase the antenna bandwidth. This has a significance to improve the performance of the VLF transmit antenna and increase the antenna work safety.