Abstract: To achieve the gain consistency and gain flatness of an ultra wideband variable gain amplifier in ultra wideband, a gain control unit is required to ensure the wide gain variation range mean and adjust the gain flatness. In this paper, a dynamic signal feedback gain control circuit based on PIN diode was proposed and the PIN diode was used as the variable impedance of the gain feedback to implement dynamic signal gain control. The serial inductor and capacitor formed the band-pass filter to select the frequency band needed to adjust its gain. Furthermore, the equivalent circuit model of PIN diode was established and the equivalent impedance parameter under different frequencies was determined by e-function fitting. The dynamic feedback adjustment mechanism of the control circuit was analyzed by using the high frequency equivalent small signal model of the dynamic signal feedback circuit. Result shows that the dynamic gain feedback control circuit can adjust the gain of the frequency band, which has large gain fluctuation to keep the whole frequency band in a consistent range. As the same time, the dynamic gain feedback can maintain a good gain flatness for each variable gain.