The invention discloses a device for multiple calibration and background extraction in target radar scattering cross section (RCS) measurement and a signal processing method thereof. The invention provides a new calibration member appearance design. By means of a designed novel calibration member (SCAM), just through one 360-DEG direction rotation measurement, data required for background auxiliary measurement, extracting and counteracting processing, and RCS multiple calibration measurement and processing can be simultaneously obtained. The novel calibration member (SCAM) provided by the invention realizes an improvement on the appearance of an existing CAM calibration member and furthermore eliminates inherent defects in background extraction auxiliary measurement and RCS calibration processing by an international universal traditional cylindrical calibration member and a CAM calibration member.