The invention discloses a variable gain low-noise driving amplifier. The amplifier has a fully differential cascode structure, wherein a common gate consists of three side-by-side silicon germanide bipolar transistors; the central silicon germanide bipolar transistor adopts parallel capacitive feedback, a reasonable input/output matching circuit is adopted, a high variable gain is provided for a circuit, and the noise coefficient is reduced; a cascade circuit provides a high variable gain and increases the reverse isolation of the circuit at the same time; and a common source amplifying circuit further improves the gain of the circuit. By controlling the selection of an external bias, the variable gain with a 3dB step length is obtained. The variable gain low-noise driving amplifier has the characteristics of high variable gain, low noise and low power consumption.