The geophone array in field data acquisition can suppress both the regular interference noise and the scattering interference noise. The regular interference noise is mainly suppressed by directional effect,while the scattering interference noise is mainly suppressed by statistical effect. Relevant theories hold that, when other factors remain fixed, the more geophones are used, the better results are obtained. It seems therefore that more geophones should be used to improve the seismic data quality; nevertheless, the authors' studies have proved that, if the number of geophones in a liner array whose sensitivities are suitably weighted is more than " +3"(where =effective-array-length /minimum-wavelength of regular interference noise), no obvious advantage can be seen by using more geophones. On such a basis, by calculating rose diagrams, the suitable number of geophones in an area-geophone-array or smearing can be pointed out, which is more economical. On the other hand, for the purpose of attenuating environmental noise, the more geophones are used in an array, the better result can be obtained under the condition that the effective array length is fixed. However, when the number of geophones reaches a certain level, no obvious improvement can be made. In addition,the authors' study also shows that the number of geophones has no definite relationship with the couple resonance noise. If the number of geophones in array is to be fixed, the geophone pattern should be taken into account. If the geophone pattern is unsuitable, adding geophones will not be beneficial to the noise attenuation. If the geophone sensitivity is not reasonably distributed, it cannot be helpful to the noise attenuation.