Based on POI（points of interest) data and spatial analysis using ArcGIS software, the spatial accessibility of four types of public service facilities preferred by the old and young groups were studied and screened, and the accessibility and the degree of matching of supply and demand of public service facilities in the main urban area of Lanzhou City were calculated. The results show that walking accessibility as a whole shows the distribution characteristics of "lower circles, stronger in the east and weaker in the west"; public transportation accessibility as a whole is better, and most of the street residents can satisfy the demand for recreation, medical care, and transportation within 20 minutes of public transportation. The accessibility of cultural and leisure facilities is poor, and the proportion of areas accessible in 15 minutes by walking and public transportation is small. The distribution of facilities is highly correlated with the distribution of residential districts, with the old city as the center of concentration, and decreasing along with the expansion of urban circles to the edges. The matching relationship between supply and demand of leisure facilities varies significantly, showing diverse characteristics. On this basis, the spatial optimization strategy of public facilities in the main urban area is proposed, in order to provide suggestions for the construction of facilities demanded by the old and weak groups.