A device for diagnosing a fault in a bearing of a motor, comprising: a current signal acquisition unit, a residual signal acquisition unit, a fault feature extraction unit and a fault diagnosis model unit, wherein in a case that the device operates in a fault diagnosis mode, the current signal acquisition unit is configured to acquire a real-time current signal of the motor; the residual signal acquisition unit is configured to extract harmonic signals from the real-time current signal of the motor acquired by the current signal acquisition unit, and remove a fundamental signal and a harmonic signal from the real-time current signal of the motor, to acquire a residual signal; the fault feature extraction unit is configured to analyze the residual signal acquired by the residual signal acquisition unit in both time domain and frequency domain, characterized in that the fault feature extraction unit is further configured to extract a fault feature vector of the bearing, wherein the fault feature vector comprises an amplitude of a fault feature frequency sequence of the bearing, a maximum value, a peak-to-peak value and a crest factor of the amplitude of the fault feature frequency sequence of the bearing, and a minimum value and an effective value of the residual signal; and the fault diagnosis model unit is configured to perform, by using a bearing fault diagnosis model obtained through training, pattern recognition on the fault feature vector of the bearing extracted by the fault feature extraction unit, to diagnose a fault state of the bearing, wherein, in the case that the device operates in the fault diagnosis mode, the fault feature extraction unit is configured to: acquire a minimum value ( I _ min) and an effective value ( I _rms) of the residual signal, acquire a fault feature frequency of the bearing, and acquire a fault feature frequency sequence of the bearing, wherein FFT transformation is performed on the residual signal to acquire a frequency spectrum of the residual signal, and acquire an amplitude of the fault feature frequency sequence of the bearing based on the frequency spectrum of the residual signal; and acquire a maximum value ( I _ f _max), a peak-to-peak value ( I _ f _peark) and a crest factor ( I _ f _ crest) of the amplitude ( I _ f ( n)) of the fault feature frequency sequence of the bearing. the current signal acquisition unit is configured to acquire a real-time current signal of the motor; the residual signal acquisition unit is configured to extract harmonic signals from the real-time current signal of the motor acquired by the current signal acquisition unit, and remove a fundamental signal and a harmonic signal from the real-time current signal of the motor, to acquire a residual signal; the fault feature extraction unit is configured to analyze the residual signal acquired by the residual signal acquisition unit in both time domain and frequency domain, characterized in that the fault feature extraction unit is further configured to extract a fault feature vector of the bearing, wherein the fault feature vector comprises an amplitude of a fault feature frequency sequence of the bearing, a maximum value, a peak-to-peak value and a crest factor of the amplitude of the fault feature frequency sequence of the bearing, and a minimum value and an effective value of the residual signal; and the fault diagnosis model unit is configured to perform, by using a bearing fault diagnosis model obtained through training, pattern recognition on the fault feature vector of the bearing extracted by the fault feature extraction unit, to diagnose a fault state of the bearing, wherein, in the case that the device operates in the fault diagnosis mode, the fault feature extraction unit is configured to: acquire a minimum value ( I _ min) and an effective value ( I _rms) of the residual signal, acquire a fault feature frequency of the bearing, and acquire a fault feature frequency sequence of the bearing, wherein FFT transformation is performed on the residual signal to acquire a frequency spectrum of the residual signal, and acquire an amplitude of the fault feature frequency sequence of the bearing based on the frequency spectrum of the residual signal; and acquire a maximum value ( I _ f _max), a peak-to-peak value ( I _ f _peark) and a crest factor ( I _ f _ crest) of the amplitude ( I _ f ( n)) of the fault feature frequency sequence of the bearing. acquire a minimum value ( I _ min) and an effective value ( I _rms) of the residual signal, acquire a fault feature frequency of the bearing, and acquire a fault feature frequency sequence of the bearing, wherein FFT transformation is performed on the residual signal to acquire a frequency spectrum of the residual signal, and acquire an amplitude of the fault feature frequency sequence of the bearing based on the frequency spectrum of the residual signal; and acquire a maximum value ( I _ f _max), a peak-to-peak value ( I _ f _peark) and a crest factor ( I _ f _ crest) of the amplitude ( I _ f ( n)) of the fault feature frequency sequence of the bearing.