Abstract：Seismic geophone tailcone is improved so as to enhance the coupling between geophone and ground and then to reduce the absorption attenuation of high frequency signal in surface low-velocity layer. To speak exactly，the geophone tailcone is lengthened to ameliorate geophone's detection of effective waves and to favour acquisition and fidelity of high frequency signals.Detection mechanism of long tailcone geophone is analysed minutely in theory.This analysis says that tailcone lengthening results in stacking effect. The theoretical derivation of frequency curve of geophone tailcone came to the conclusions that suppression degree which stacking effect exerts on high frequency signals has something to do with tailcone length and velocities in surface layer and tailcone material，and that stacking effect is very unfavourable to both widening an useful receiving frequency band of geophone and protecting high frequency signals.
