Studies have shown that in lower limb movement category, imagine eeg signals based on the motion to imagine joining steady-state somatosensory evoked potentials can get higher classification results, but most studies are based on double side auxiliary body feeling potential induced by electrical stimulation, the unilateral electrical stimulation auxiliary study is less, in this paper, the unilateral posterior tibial nerves and bilateral ankle ankle posterior tibial nerve stimulation, respectively To find out what kind of stimulus can get better classification results. Two control experiments were designed: unilateral left foot electrical stimulation mode vs unilateral right foot electrical stimulation mode and unilateral right foot electrical stimulation mode vs bilateral simultaneous electrical stimulation mode. Based on the analysis of the characteristics of spectrum, time-frequency map and brain topography, it was concluded that the ERD characteristics of the unilateral right foot electrical stimulation mode were the most significant and the activation degree was the deepest. The average classification accuracy of unilateral right foot stimulation mode was 5.57% higher than that of dual stimulation mode, and the classification accuracy of single subject's unilateral right foot stimulation mode was 15% higher than that of dual stimulation mode, which proved that the assistance of unilateral right foot electrical stimulation is more conducive to the classification of lower limb motor imagination EEG signals.