Objective: To evaluate influences of multimorbidity on health expenditure of urban poor families. Methods: A total of 2300 poor families were surveyed with a self-designed questionnaire. Kruskal-Wallis Test，Linear Regression and Quantile Regression were used to assess the impact. Results: The per capita expenditure on chronic treatment for households with members with chronic co-morbidities increased by 20.95 %compared to households with members suffering from 1 chronic disease; at the 10 th25 th50th75th and 90th percentiles，the per capita expenditure on health care for households with members with chronic co-morbidities increased by 32.68 %，32.65 %，30.70 %，32.89 %and 32.72 %compared to households without members with chronic diseases，and household health expenditure as a proportion of total expenditure increased by 5.12 %，7.97 %，13.56 %，18.94 %and 21.60 %respectively. Conclusion: The multimorbidity increases the chronic disease treatment expenditure and health expenditure of poor families. The proportion of family medical and health expenditure in total expenditure has been increased，and other household expenditures have been squeezed out. Therefore，efforts should be made to improve the outpatient security of multimorbidity，establish expenditure based medical assistance system，strength community management and self-management of multimorbidity.