The invention relates to the field of squeezed state optical field quantum noise measurement. A low-frequency low-noise balanced homodyne detector includes a differential circuit composed of two photodiodes, a bootstrapping current-voltage conversion circuit composed of two bumpers and a trans-impedance operation amplifier (5), and an AC and a DC output circuit composed of a first capacitor (6) and a first resistor (7) separately. According to the invention, through quantitative analysis of input current total noise of the low-frequency low-noise balanced homodyne detector in a low frequency band and since a sampling resistor in a traditional detector is removed and the bootstrapping current-voltage converter is adopted, the electronic noise of the low-frequency low-noise balanced homodynedetector within a frequency of 20 Hz to 200kHz is reduced substantially and requirements for high gain, high common-mode rejection ratio, simple structure and low cost are met.