A speed detection system of a passenger conveyor comprising: an imaging sensor and/or a depth sensing sensor configured to sense at least one part of the passenger conveyor to acquire sequence frames; and a processing apparatus configured to analyze the sequence frames to obtain at least speed information about steps of the passenger conveyor, which comprises: an optical flow estimation module configured to calculate, based on an optical flow method, a shift of a corresponding feature point between any adjacent frames in the sequence frames in frame coordinates; a time calculation module configured to determine a time quantity between any adjacent frames in the sequence frames; a speed calculation model; characterized in that the processing apparatus further comprises: a calibration module configured to convert the shift of the feature point in the frame coordinates to a shift in three-dimensional space coordinates; and in that the speed calculation model is configured to obtain by calculation, based on the shift of the feature point in the three-dimensional space coordinates and the corresponding time quantity, speed information of time points corresponding to any adjacent frames, and further combine the speed information to obtain speed information of the sequence frames. an imaging sensor and/or a depth sensing sensor configured to sense at least one part of the passenger conveyor to acquire sequence frames; and a processing apparatus configured to analyze the sequence frames to obtain at least speed information about steps of the passenger conveyor, which comprises: an optical flow estimation module configured to calculate, based on an optical flow method, a shift of a corresponding feature point between any adjacent frames in the sequence frames in frame coordinates; a time calculation module configured to determine a time quantity between any adjacent frames in the sequence frames; a speed calculation model; an optical flow estimation module configured to calculate, based on an optical flow method, a shift of a corresponding feature point between any adjacent frames in the sequence frames in frame coordinates; a time calculation module configured to determine a time quantity between any adjacent frames in the sequence frames; a speed calculation model; characterized in that the processing apparatus further comprises: a calibration module configured to convert the shift of the feature point in the frame coordinates to a shift in three-dimensional space coordinates; and in that the speed calculation model is configured to obtain by calculation, based on the shift of the feature point in the three-dimensional space coordinates and the corresponding time quantity, speed information of time points corresponding to any adjacent frames, and further combine the speed information to obtain speed information of the sequence frames. a calibration module configured to convert the shift of the feature point in the frame coordinates to a shift in three-dimensional space coordinates; and in that the speed calculation model is configured to obtain by calculation, based on the shift of the feature point in the three-dimensional space coordinates and the corresponding time quantity, speed information of time points corresponding to any adjacent frames, and further combine the speed information to obtain speed information of the sequence frames.