Time domain features of slow potentials ≤2 Hz) during periodic movement and motor imagery at fast and slow (4 Hz and 2 Hz) were investigated in 4 healthy subjects by event-related potentials in the paper. EEG was recorded from 64 electrodes and 9 closely spaced electrodes overlaying the left and right sensorimotor area were analyzed. The subjects performed 40 fast and 40 slow (paced by metronome) movement and motor imagery of six tasks that involved three limbs (left and right index fingers and right toes) at first-person perspective. In addition, the subjects also performed motor imagery involved left and right arms and feet at third-person perspective. Based on brain processing mainly involved with the slow potentials during periodic movement and motor imagery, event-related potentials were low-pass filtered with 2 Hz cut-off frequency (24 dB/oct). At C1, Cz, and C2, fast movement-related potentials had a larger positive slow potentials tendency than slow movement-related potentials 1.5 s after movement onset. In contrast to movement, slow motor imagery-related potentials had a larger positive slow potentials tendency than fast motor imagery-related potentials 1.75 s after motor imagery onset at these electrodes. Time delays reaching positive peak and rebound rate after peak were also explored. These results may be very important for further exploring relationship between speed and EEG activity during periodic movement and motor imagery. The study may provide a strategy to realize fine control of robots by brain-controlled robot interface.