Abstract: Population is an important support for economic and social development, and the impact of an ageing population on the service sector has become an unavoidable issue in quality development. Based on panel data of 110 cities at prefecture level and above in the Yangtze River Economic Belt from 2010 to 2020, the impact of population ageing on the optimization and upgrading of service industry from the perspective of structural efficiency, and the heterogeneity of different regions and at different rates of ageing is analysed. The results show that: (1) Population ageing has a significant positive impact on the producer services and efficiency enhancement of the service industry, while it has a significant negative impact on the high-end of the service industry. (2) The significant inhibiting effect on the producer services and efficiency improvement of the service industry is mainly concentrated in the upper and lower reaches of the Yangtze River Economic Belt, while the positive effect on efficiency improvement is seen in the lower areas. (3) The slow growth rate of the ageing population will have a more pronounced deterrent effect on the producer services, while the accelerated ageing process will promote the development of the high-end of the service industry and have a certain impact on production efficiency. To this end, there is an urgent need to focus on the impact of the ageing population on the structure and efficiency of the service industry in the Yangtze River Economic belt at both the supply and demand levels, and to promote the high-quality development of the service sector in accordance with local conditions and the process of transformation and application of technological achievements.