The Einstein Probe (EP) mission is a small scientific satellite dedicated to time-domain high-energy astrophysics. It aims at discovering transients and monitoring variable objects in 0.5-4 keV X-rays, for which it will employ a large instantaneous field-of-view (60°×60°, or ~1 steradian), along with moderate spatial resolution (FWHM ~5arcmin) and energy resolution. It will also carry a follow-up observation X-ray telescope with a smaller field-of-view (1°×1°) — capable of much larger light-collecting power and better energy resolution than the main survey telescope. Public transient alerts will also be issued rapidly, in order to trigger multi-wavelength follow-up observations from the world-wide community. Its wide-field imaging capability is achieved by using established technology of novel micro-pore “lobster-eye” optics, thereby offering unprecedentedly high sensitivity and large Grasp superseding previous and existing X-ray all-sky monitors and survey missions. Einstein Probe has been selected as a missions for advanced studies under the pilot space science programme of the Chinese Academy of Sciences