Abstract: Extrinsic chirality in metasurfaces offers a novel approach for angle-dependent electromagnetic wave manipulation, yet the control efficiency remains to be improved. This paper presents a new method for high-efficiency control of terahertz angular dispersion and circular dichroism using reflective metasurfaces with extrinsic chirality. We propose non-chiral meta-atoms with a single mirror-symmetry axis that enhance the response efficiency by leveraging multiple interference effects in a metal-insulator-metal structure. Under oblique incidence, an ultra-strong terahertz circular dichroism with an absolute value of approximately 0.8 is observed, where the absorption efficiency of the single circularly polarized component reaches up to 98%. The circular dichroism of reflected terahertz waves can be effectively adjusted by changing the magnitude and direction of the incident angle, in-plane orientation of the meta-atoms, and their geometric dimensions. Additionally, based on the strong extrinsic chirality and angular dispersion of the proposed metasurfaces, we demonstrate an angle-dependent terahertz polarization conversion scheme, effectively altering the ellipticity and azimuth angle of the reflected wave and achieving a wide dynamic range of polarization modulation. The proposed metasurface platform provides new insights for designing reflective terahertz devices.