Interlayer interference exists commonly during the development of multilayer sand reservoirs. Research into the mechanisms and countermeasures of interlayer interference has been undertaken from various perspectives by many scholars. However, the degree of understanding and its applications are less than adequate. Therefore, it is necessary to further quantitatively analyze and discuss interlayer interference in depth. The phenomenon of the interlayer interference is firstly identified with the production capacity testing of oilfield production wells. Then the simulations of the well productivity testing considering threshold pressure gradient are conducted to deepen the understanding of the producer interlayer interference. Next, the mechanisms of the producer interlayer interference are revealed based on a multiple factor analysis. Finally, an understanding of reservoir vertical heterogeneity is proposed and the way to characterize the reservoir heterogeneity is discussed. This study provides a strong theoretical basis and technical guidance to improve productivity prediction accuracy and make more precise development strategies for multilayer sand reservoirs.