Abstract:Seismic geophone string suffered from outsideelectromagnetic induction interference inevitablywhen conversing the noise-bearing synthetic seis-mic wave signals into electric signals, mainly inclu-ding magnetic field interference and electric fieldinterference, both of them are common mode sig-nals. Known from the analysis of equivalent circuitof magnetic field interference, reducing magneticfield interference can be implemented by two ap-proaches:increasing the distance from interferentsource to useful signal circuit and reducing the re-turn circuit area of useful signal. Known from a-nalysis of circuit equivalent of electric field inter-ference, the interference of electric field can be re-duced by the balancing design of circuit. Current-ly, geophone string is used in a majority of seismicexploration, in which the geophone distance islarge. It is discovered by analysis of signals of geo-phone string acquired from PXI industrial micro-computer of American NI Company that the unbal-ance of geophone string is main reason of interfer-ence invading, which mainly showed in unbalanceof ground capacitance, and unequal length of wirefrom positive/negative poles of geophone to inputterminal of acquisition unit is direct representationof unbalance of ground capacitance. Lengtheningthe connecting wire of negative pole of geophoneuntil to equal to the length of connecting wire ofpositive pole and designing the balancing geophonestring can effectively reduce the interference ofcommon mode signal, improving the antijammingcapacity of seismic geophone string, which is alsoproved by experiments.