Abstract: In response to the threat of near-Earth asteroid impacts,the short-term warning capabilities of various typical ground-based and space-based optical observation systems for near-Earth asteroids (NEAs) were analyzed. The concept of short-term warning circle was proposed. Using the visible reflection model of celestial bodies in the solar system,the short-term warning capabilities of large-aperture ground-based telescope LSST,and three typical space-based telescopes deployed in the orbits of Sun-Earth L1 point,Venus-like orbit and distant retrograde orbit were simulated and calculated and the early warning capabilities of three space-based systems for NEAs approaching from the direction of the sun were compared. The results show that the early warning capability of L1 was good but the available warning time was short relatively; the Venus-like orbit constellation had a long warning time and wide coverage area,but the existence of phase gaps would cause a big omission probability; distant retrograde orbit had the advantages of high coverage rate and long warning time to the NEAs from the direction of the sun. The deployment of several space-based telescopes can provide sufficient supplement to the ground-based observation system,solve the problem of coverage omission in the direction of the sun,and provide approaching warning of NEAs in all directions.