Under the developing trends of population aging and old aging, China is trying to establish an endowment pattern of "with family endowment as the basis, with community endowment as the reliance, and with institutional endowment as the support". Compared with other endowment patterns, endowment institutions possess the features of specialization and standardization, and the most important factor to evaluate endowment institutions is the quality of service. In this thesis, GAP model will be adopted to analyze the sources of quality problems which exist in endowment institutions' long-term care service from the perspective of five sources of service quality gap, and the preliminary countermeasures will also be proposed. According to the "Statistical Bulletin of Social Service Development in 2013 " issued by Ministry of Civil Affairs, by the end of 2013, all over the country, the number of elderly population over 60 years old was 202.43 million, accounting for 14.9% of the total number of population. Among them, the number of elderly population over 65 years old is 131.61 million, which accounts for 9.7% of the total number. All together, there were 42,475 endowment service institutions, and 4.937 million beds in China, 18.9% higher than 2012. Ell Compared with other endowment patterns, endowment institutions possess the features of specialization and standardization. In the endowment institutions, the long-term endowment care service system, whose starting points are the demands of elderly people and whose duration time is longer than six months, is formed by comprehensive long-term care service-oriented architectures, including basic long-term endowment care service (such as care for catering and daily life, health care service, psychosocial service, etc.), long-term endowment care human resources, long-term endowment care service system, and long-term endowment care policy support. The core evaluation index of long-term endowment care service system is its service quality.