Abstract: This paper focuses on the study on the effectiveness of earthquake early warning system and social benefits from the perspective of earthquake early warning system’s reducing the casualties and the economic losses. Based on the calculation results of the annual average occurrence probability of potential earthquakes in each magnitude grade in Lanzhou city and its surrounding areas， we calculated the effective warning time and seismic intensity by using the data from 80 earthquake early warning stations in Lanzhou region. Based on the life-vulnerability model， we calculated the casualties coefficient by the early warning system， and then calculated the economic losses by the macro GDP loss assessment method. The results show that it is crucial for improving the efficiency of earthquake early warning to minimize the scope of blind areas. The construction of earthquake early warning system and the layout of station network should focus on the population density， the economic situation and the probability of earthquake occurrence of the layout areas.