In order to study flood control problem in the tail of Ganjiang river，water level was studied based on Ganjiang River network model under changing conditions which were caused by engineering measures，such as plugging measures、regulation measures.The results showed that：when the north branch was plugged，water levels in branches were risied which lead a negative effect on flood control.When regulation measures were implemented，conveyance capacity of south branch was improved，water levels in most reaches falled during the flood period，which lead a positive effert on flood control.But the reduction is within 0.1 meters，the effect caused by that were limited.