On the base of the data of Sheshan seismic testing array in Shanghai, the features of frequency and amplitude of noise, near event and far event are studied. Some factors affecting correlation among the records of substations in the array are discussed. With the distance between substations getting longer, the co rrelation tend to be smaller; with the distance fixed, the correlation depends on single frequency, epicentral distance (angle of incidence), and the noise vibration. Wiener single-channel frequency filters are not best to use in filtering original data for beam-form. The filters would be designed not only to depress noise but also to keep the well correlated signals in order to beam-form better.