Nanopore electrochemistry achieves the single-molecule measurement based on the electrochemically confined effect.The detection of picoampere-level current signals with milli-second duration makes a great challenge for the electrochemical instruments,which requires not only low noise and high current resolution,but also high bandwidth for capturing the rapid signals.A portable Cube ultrasensitive nanopore instrument consisting of a frequency compensation circuit,a pre-amplifier measurement system and a field programmable gate array (FPGA) based high-speed digital processing circuit has achieved the ultra sensitive electrochemical measurement with high temporal resolution,high current resolution and rapid acquisition of weak current signals.In this study,the stability of this instrument was tested by utilizing a high resistance resistor.Compared with the commercial instrument,the noise root mean square(RMS) values of the current baseline obtained with the Cube ultrasensitive nanopore instrument were reduced by 80.0%,87.5% and 48.2% under the cut-off frequencies of 5,10 and 100 kHz,respectively.Therefore,the Cube ultrasensitive nanopore instrument has a strong ability to suppress noise,offering a better current resolution.Results showed that the deviation of the applied voltage of the instrument was only 0.14% of the applied voltage change(10 mV),verifying a negligible error for the applied voltage of this Cube instrument.An Aerolysin nanopore detection of Poly(dA)4 under different applied voltages demonstrated that the error of residual current blockage was less than 0.01 when both the Cube and commercial instrument were used.Therefore,the Cube ultrasensitive nanopore instrument was suitable for the single molecule detection with high stability,high sensitivity and strong portability.