High-precision signal digitization device and method with ultralow phase jitter

The present invention discloses a high-precision signal digitization device and a high-precision signal digitization method with ultralow phase jitter. The high-precision signal digitization device comprises a voltage control variable gain amplifier, an automatic gain controller, an automatic gain and voltage-controlled gain switch, an analog-digital converter for achieving digitization of a measured signal, an automatic gain voltage digitizer, a voltage-controlled voltage converter and a processor, wherein the automatic gain and voltage-controlled gain switch is connected with the output end of the automatic gain controller, and the output end of the automatic gain controller is connected with the automatic gain voltage digitizer. According to the high-precision signal digitization device of the present invention, amplification amount required by an amplifier is obtained through adoption of the automatic gain controller, a control voltage required by the amplifier at the amplification amount is measured, then a required fixed control voltage is provided, thereby ensuring high precision of digitized measured data, and avoiding phase noise caused by continuous adjustment for amplification amount of the amplifier.