The invention discloses a signal conditioning circuit, a conditioning method thereof and a double sampling retaining circuit. The signal conditioning circuit comprises a first chopping switch, a programmable gain amplifier, a second chopping switch, a double sampling retaining circuit, an analog-to-digital converter, and a digital reduction sampling filter which are connected in sequence. The double sampling retaining circuit samples outputs of the programmable gain amplifier in two-phase positions of a chopping clock, and the results of two samplings are added. and an added output voltage is transmitted to and processed by the analog-to-digital converter, and the digital reduction sampling filter. Since the double sampling retaining circuit is added, the invention avoids the residual and off-tune problem in a chopping amplifier. Meanwhile, the invention facilitates the integration of a single chip, without the need of external filtering capacitor. Furthermore, a novel sequential control reduces the consumption of a digital signal conditioning circuit based on a chopping amplifier.