The invention discloses an oil production method for a horizontal well. The method comprises the following steps of using a horizontal well staged fracturing technology for performing staged fracturing on a reservoir to form N artificial fractures communicated with a horizontal well, wherein the M-th artificial fracture is in adjacent to the (M+1)-th artificial fracture, and the M-th artificial fracture is nearer to a wellhead of the horizontal well than the (M+1)-th artificial fracture; performing setting on the horizontal well between the N-th artificial fracture farthest to the wellhead of the horizontal well and the (N-1)-th artificial fracture; injecting water into the N-th artificial fracture through an oil pipe; performing oil production through a casing pipe; performing unsetting after the oil production is completed; respectively performing setting on the horizontal section of the horizontal well between the M-th artificial fracture and the (M+1)-th artificial fracture, and the horizontal section of the horizontal well between the (M-1)-th artificial fracture and the M-th artificial fracture; and performing oil production through the casing pipe after the water injection into the M-th artificial fracture through the oil pipe. The method has the advantage that the same-well water injection and same-well oil production can be realized through one horizontal well.