The invention relates to the radio frequency low noise amplifier from the single end to the difference mode with variable gain belonging to the area of receiver technique in the wireless communication. The amplifier includes main amplifier circuit with single input end, the output buffer from the single end to the difference mode, which is connected to the outupt and input ends respectively, and the variable gain unit. The main amplifier consists of the 2 MOS tubes, 3 inductors. The buffer is composed of 3 MOS tubes, 2 inductors and 1 capacitor. The variable gain unit consists of 2 MOS tubes,2 resistors, capacitors and diodes. The invention provides the advantages of lowering the power consumption, improving the noise, removing the noise induced by the balum, controlling the gain as wellas lowering the requirement of the dynamic range for next stage.