This disease is mainly caused by retention of blood stasis in the thoroughfare and conception vessels as well as the uterus. Blood stasis is caused by emotional depression, inhibited flow of liver qi, obstructed activity of qi, unsmooth circuation of blood and qi stagnation; abdominal mass results from stagnation of qi and blood due to excessive intake of uncooked and cold foods or attack by exogenous pathogenic cold which coagulates blood. Constitutional asthenia of spleen qi and hypofunction in transporting blood will slow the flow of blood and gradually lead to stasis. Retention of blood stasis in the thoroughfare and conception vessels as well as uterus blocks uterine collaterals and causes dysmenorrhea.