Objective: In order to validate the effectiveness of methods of defining poverty caused by illness which are based on catastrophic health expenditure and impoverishment health expenditure, originated from relative costs theory.Results: This paper uses empirical approach to explore the definition methods by comparing the original methods with modified methods and defined population with the actual situation of poverty alleviation.Results: Study results show that the catastrophic health expenditures incurred ratio is about 20% and shows the aggregation of both low-income and high-income groups.The impoverishment health expenditure incurred ratio is about 12% and they mainly are families at the edge of poverty line.This study found that 70% of the families defined based on our method did not receive medical assistance in reality.Conclusion: Therefore, the definition methods based on relative costs theory are of great value in Chinese medical assistance systems for defining poverty caused by illness.Grouping based on household ability to pay could improve the methods' operability and effectiveness.