Abstract: Injection intensity, especially injection allocation rate of each well group, is critical given the timing and mode of water injection. Rational single well injection allocation rate can effectively relieve the areal, interlayer and in -layer contradictions, maintain the formation pressure, enlarge the swept volume, effectively control the increasing of water cut, and improve the development effects and oilrecovery factor of waterflooding oilfield. Based on a comprehensive analysis and study of the current available injection allocation methods in China, it is proposed to take the injector-group as the study unit and use the correlation coefficient from normalization of the degree of association in grey correlation analysis as the dynamic proration coefficient of the producer in the well group, so as to calculate the injection allocation rate of the injector in the well group based on proration of the liquid producing capacity of the producers. A case trial calculation shows that it is simple and practical and can be used as a routine injection allocation method.