Abstract: Space-based monitoring and early warning of Near-Earth Asteroids (NEAs) is an important development direction for future planetary defense. Cooperative space-and ground-based observations can give full play to the advantages of space- and ground-based telescopes and improve the efficacy of the system as a whole. In this paper, a model of near-Earth asteroid observation was formulated, a scheme of space-based observation system for Sun-Earth L1 point orbit was analyzed and designed, and an efficacy evaluation method was proposed. The cooperative observation efficacy of the Sun-Earth L1 point orbit observation system was simulated and evaluated based on the potentially hazardous asteroids database. The relevant early warning efficacy was calculated and analyzed, and the design concept of regional and time-domain divided collaborative observation was proposed. This paper provides importance reference for future evaluation of the efficacy of different space-based observation systems and the study of space- and ground-based cooperative observations. The preliminary simulation results show that the infrared and visible systems of the Sun-Earth L1 point orbit can achieve 49.4% and 38.2% cataloging completeness of the potentially hazardous asteroids in 1 year with a limited apparent visual magnitude of 22, and both can carry out the monitoring mission well; after cooperative observation with ground-based station, the completeness rate of the corresponding cooperative system can reach 58.9% and 50.6%, respectively, which is 1.19 times and 1.35 times that of the completeness rate before, indicating that cooperative observation can effectively improve the observation efficacy of the system.