The main effect factors of production decline rate in water drive reservoir have great significance for productivity analysis and development adjustment. The Grey interconnect analysis method is used in two aspects. One is to decide the main factor which have great effect on the production decline rate in water flooding reservoirs, the other is to select the main wells which have great effect on the main factor. On the first aspect, the affecting factors which are independent and have direct influence on the decline rate are normalized respectively. Then the interconnect sequence of the affecting factors are obtained by using the Grey interconnect analysis method. On the second aspect, the water cut is taken as the reference sequence, the main wells are selected by using the Grey interconnect analysis method. Application in oil field verifies the effectiveness of the method. The results shows that the Grey interconnect analysis method can adapt to the features of the more influence factor and the larger date size, and the good reslut can be obtained in the application of the analysis and trace for the production decline rate in water flooding reservoirs.