The invention relates to a low-frequency fully differential Gm-C filter applied to ECG signal acquisition. And the filter comprises a transconductance unit, a capacitor C1, a capacitor C2, a capacitorC3 and a capacitor C4, and the transconductance unit comprises a fully differential transconductance unit Gm1, a fully differential transconductance unit Gm2, a fully differential transconductance unit Gm3, a fully differential transconductance unit Gm4 and a fully differential transconductance unit Gm5. The improved source electrode negative feedback circuit is adopted, common-mode voltage on aresistor is effectively eliminated, the upper limit of input common-mode voltage is prevented from being reduced, and it is convenient to achieve that the output common-mode voltage is equal to the input common-mode voltage; The pseudo full-differential circuit based on the series-parallel current mirror is adopted, and a common-mode feedback circuit of a traditional full-differential circuit is prevented from being used for determining the output common-mode voltage, so that the complexity of circuit design is reduced, and the power consumption is reduced.