With the continuous growth of global energy demand, the development of oil and gas resources faces critical challenges such as low reserve control, weak single-well productivity, and low recovery efficiency. To address these issues, hydraulic fracturing of horizontal wells has been widely applied in low-permeability reservoirs and has demonstrated remarkable production enhancement. However, due to strong formation heterogeneity and the presence of interbeds, fractures may extend across layers during the fracturing process, leading to potential interlayer interference. This phenomenon can significantly affect fracture effectiveness, production performance, and development efficiency. In this study, a coupled fracture propagation and well test interpretation framework is proposed to determine whether hydraulic fractures penetrate interlayer boundaries and induce interlayer communication in fractured horizontal wells. A mathematical model of fracture propagation is first established to simulate the vertical extension behavior of fractures near interlayer interfaces. Subsequently, well test analysis and numerical history matching are employed to evaluate pressure transient responses and identify signatures of interlayer interference. The results indicate that the proposed model can effectively identify whether fracture penetration and interlayer communication occur after hydraulic fracturing. The agreement between numerical simulation and well test interpretation demonstrates the reliability of the proposed method. This study provides a practical approach for diagnosing interlayer interference in fractured horizontal wells and offers guidance for optimizing fracturing design in tight oil reservoirs.