A growing aging population，disabled population，and the disorder expansion of medical expenses threaten the sustainable development of the healthcare security system. Based on the data from China Health and Retirement Longitudinal Study in 2011，2013，2015，and 2018，this study used the Differences-in- Differences to explore the effect of long - term healthcare insurance on outpatient utilization and medical expenses. The results show that long -term healthcare insurance can significantly reduce out -of -pocket medical expenses and outpatient visits. The heterogeneity analysis showed that long - term healthcare insurance had a more significant impact on urban and rural healthcare insurance participants than that of the urban workers. At the income level，long -term healthcare insurance reduced medical costs for middle and upper -income families but had little effect on low - income families. These conclusions validated the value of long - term healthcare insurance and provided a meaningful reference for the new round of medical reform and the expansion of pilot scope in China.