Abstract: Inter-fracture flow laws and fracture interaction degrees of multi-stage fractured horizontal well are of great significance to determine fracture interaction degree in the process of production and diagnose water producing fractures and water directions. Based on the Cinco-Ley finite conductivity fracture model, a hydraulic fracture was divided into several fracture micro-elements by means of the point source method. A matrix was constructed by combining internal and external boundary conditions together to calculate the flow rate of each fracture micro-element. The well testing model for the segmental pressure measurement of multi-stage fractured horizontal well was established under the constraint of the sum of the flow rates of fracture micro-elements in each testing segment. If the flow rate in each testing segment is distributed in the shape of regular U, the derivative curve is coincident with testing curve of the full hole. Compared with the testing curve of the full hole, the pressure derivative curve whose dimensionless flow rate is higher than the regular flow rate moves upward in the stages of well storage and linear flow. And otherwise, it moves downward. With the decrease of the fracture semi-length in each testing segment, the pressure derivative curve moves upward in the stage of linear flow. With the increase of the fracture interval, the stage of linear flow lasts longer. As the flow conductivity of the fracture increases, the early pressure derivative decreases, but the trend slows down. Fracture interaction occurs in the stage of second transition flow, when the pressure derivative of the testing segment in the middle of horizontal well upwarps. The coincidence between the result of the proposed semi-analytic model under the simplified conditions and the numerical well testing result of commercial well testing software is extremely high, indicating the discrete solution method is accurate and reliable. The interpretation on the segmental pressure measurement in the horizontal well case is well fitted, and the obtained parameters provide the basis for diagnosing the inter-fracture liquid producing situations of horizontal well and formulating development adjustment measures.