Abstract: The traditional matching network can only achieve the ideal matching at one certain frequency through the series inductor, which limits the antenna bandwidth. In this paper, the broadband matching problem of electrically small antenna is studied, and a negative-impedance matching network is realized by using the active non-foster circuit, which breaks the limitation of the electrically small antenna quality factor and can cancel the capacitance of the electrically small antenna in a very wide frequency band. Based on the above principle, a negative resistance matching network for handheld devices terminal antenna is designed and processed in this paper. When the height of the monopole antenna is only 1/10 wavelength, no structure is attached, the VSWR is less than 2.5 in the 400 MHz to 700 MHz band, and the antenna radiation efficiency is greater than 75%.