Objective To understand the status of diabetes cognition among COPD patients complicated with diabetes mellitus. Method Totally, 240 COPD patients complicated with diabetes mellitus were investigated by self- designed questionnaire about their knowledge of diabetes mellitus. Results There were significant differences between different gender patients in hypoglycemia symptoms and treatment principles( P 0. 01),among different age patients in diabetes mellitus causes,clinical manifestation and complications,treatment( P 0. 01 or P 0. 05). There were significant differences between among different education background patients in correlation between long- term using glucocorticoid and diabetes and diabetes treatment( P 0. 01 or P 0. 05),among different COPD stages patients in correlation between long- term using glucocorticoid and diabetes,diabetes mellitus causes,hypoglycemia symptoms and treatment principles,diabetes treatment( P 0. 01 or P 0. 05). There were significant differences between different diabetes stages patients in diabetes mellitus causes,clinical manifestation and complications,hypoglycemia symptoms and treatment principles,diabetes treatment( P 0. 01 or P 0. 05). Conclusion The diabetes related health education for COPD patients should be specific according to their situations,in order to control the glucose,promote the prognosis and improve their self- control of glucose.