The invention provides a string for horizontal well fracturing completion. The string is characterized by comprising a hydraulic ground control device, a bushing, an oil pipe arranged inside the bushing, a hydraulic line, a hanger, a plurality of fracturing construction units and a seat sealing unit at the bottom end of the string. The fracturing construction units are sequentially connected with the oil pipe in a horizontal section, and each fracturing construction unit is provided with a hydraulic packer and a hydraulic slide bushing. One end of the hydraulic line is connected with the hydraulic ground control device, and the other end thereof is connected with the hydraulic packer and the hydraulic slide bushing of each fracturing construction unit. The hydraulic ground control device provides hydraulic pressure serving as pressure change of control signals to the hydraulic slide bushings through the hydraulic line so as to open or close each hydraulic slide bushing. The invention further provides a fracturing construction method for horizontal well fracturing completion. The string is capable of achieving unlimited staged fracturing of the horizontal section without step-by-step ball feeding as well as achieving later-period staged production, thereby being extremely suitable for offshore staged fracturing.