The Closeby Habitable Exoplanet Survey (CHES) mission is proposed to discover habitable-zone Earth-like planets of the nearby solar-type stars (∼ 10 pc away from our solar system) via micro-arcsecond relative astrometry. The major scientific objectives of CHES are: to search for Earth Twins or terrestrial planets in habitable zones orbiting 100 FGK nearby stars; further to conduct a comprehensive survey and extensively characterize the nearby planetary systems. The primary payload is a high-quality, lowdistortion, high-stability telescope. The optical subsystem is a coaxial three-mirror anastigmat (TMA) with a 1.2 m-aperture, 0.44° × 0.44° field of view and 500 nm − 900 nm working waveband. The camera focal plane is composed of 81 MOSAIC scientific CMOS detectors each with 4 K × 4 K pixels. The heterodyne laser interferometric calibration technology is employed to ensure micro-arcsecond level (1 µas) relative astrometry precision to meet the requirements for detection of Earth-like planets. CHES satellite operates at the Sun-Earth L2 point and observes the entire target stars for 5 years. CHES will offer the first direct measurements of true masses and inclinations of Earth Twins and superEarths orbiting our neighbor stars based on micro-arcsecond astrometry from space. This will definitely enhance our understanding of the formation of diverse nearby planetary systems and the emergence of other worlds for solar-type stars, and finally to reflect the evolution of our own solar system.