Embodiments of the present application provide a method and a device for acquiring ECG data, and an ECG detection system. A method for acquiring ECG data, comprising: acquiring ECG signals of heart; performing a first-stage amplification on the ECG signals, a multiple of the first-stage amplification including 5 to 10 times; performing band-pass filtering process within a first frequency range on the ECG signals on which the first-stage amplification has been performed, the first frequency range being 0.1 Hz to 50 Hz; performing a second-stage amplification on the ECG signals on which the band-pass filtering process has been performed, a multiple of the second-stage amplification including 40 to 50 times; performing analog-to-digital conversion on the ECG signals on which the second-stage amplification has been performed, to generate ECG digital signals; and outputting the ECG digital signals.