Background:China has not established social security system for rare diseases.Rare diseases could easily impoverish patients and their families.Little research has studied the equity and accessibility of health services for patients with rare diseases in China.This study aimed to explore the factors that influence health expenditure of rare diseases and evaluate its equity.Methods:Questionnaire survey about living conditions and cost burden of patients with rare diseases was conducted.Individual and family information,health expenditure and reimbursement in 2014 of 982 patients were collected.The impact of medical insurance,individual sociodemographic characteristics,family characteristics,and healthcare need on total and out-of-pocket (OOP) health expenditures was analyzed through the generalized linear model.Equity of health expenditure was evaluated by both concentration index and Lorenz curve.Results:Of all the surveyed patients,11.41％ had no medical insurance and 92.10％ spent money to seek medical treatment in 2014.It was suggested female (P =0.048),over 50 years of age (P =0.062),high-income group (P =0.021),hospitalization (P =0.000),and reimbursement ratio (RR) (P =0.000) were positively correlated with total health expenditure.Diseases not needing long-term treatment (P =0.000) was negatively correlated with total health expenditure.Over 50 years of age (P =0.065),high-income group (P =0.018),hospitalization (P =0.000) and having Urban Employee Basic Medical Insurance (UEBMI) (P =0.022) were positively correlated with OOP health expenditure.Patient or the head of the household having received higher education (P =0.044 and P =0.081) and reimbursement ratio (P =0.078) were negatively correlated with OOP health expenditure.The equity evaluation found concentration indexes of health expenditure before and after reimbursement were 0.0550 and 0.0539,respectively.Conclusions:OOP health expenditure of patients with UEBMI was significantly more than that of patients without medical insurance.However,for any other medical insurance,there was no difference between OOP health expenditure of the insured patients and patients without insurance.The current reimbursement policies have increased the equity of health expenditure,but are biased toward high-income people.