Background: Health equity is systematic deprivation gaps in resource allocation, accessibility and utilization of health services. The elderly people with high prevalence of chronic, and non-communicable diseases (NCDs) usually face problems with respect to high treatment cost, and if health inequity exists, they disproportionately suffer a decrease in their quality of life. Objective: The study was aimed at exploring the factors affecting health equity in Thai elderly, as well as activities that improve health equity. We focused on horizontal equity dimensions of cost, use, and accessibility to health services. Methodology: This was a systematic review, searching 5 Thai and 2 international databases. The inclusion criteria covered equity in health in elderly and related meanings (in Thai and English). Content analysis, and descriptive presentation were used in this review. Result: The affecting factors to inequity in health included external factors (e.g. socioeconomic factors) and internal factors (personal/behavioral factors on use of service). The external factors that improved equity in health in elderly included health insurance coverage and living in urban area. The external factors that decreased equity in health in elderly included education lower than high school level, low income, no occupation, no insurance and living in rural or remote area. The internal factors that decreased equity in health in elderly included 1) having disability or chronic illness, 2) stress, and 3) behavior for not using health service. All of these factors affected on 1) health status, 2) health financing, and 3) health needs (accessibility and utilization). The interventions that decreased inequity in health and improved equity in health were as follows: 1) treatment and rehabilitation activities at secondary and tertiary hospitals, 2) health promotion and disease prevention activities at the community or primary care units, and 3) public services or social welfare activities aimed at reducing inequity by decreasing health service expenditure to elderly. Recommendation: Appropriate approaches amending factors and activities affecting inequity should be implemented to achieve health equity in elderly.