Abstract: In viewing the problem that existingent test methods can’t accurately detect water production layers in low production horizontal wells in the tight reservoirs of Changqing Oilfield,water production detection strings for low production horizontal wells have been designed for different formation pressures as well as bridge plug and packer plugging string according to the different water production section.Two kinds of water test strings have been applied in 21 wells,and two kinds of water plugging strings for low production horizontal wells have been applied in 22 wells in Changqing Oilfield,with a water layer identification efficiency of 96.7% and the successful water plugging rate of 81.8%.This showed that water test string could accurately identify watered production layers,and water plugging string could effectively perform water plugging at different water production secion in low production horizontal wells.