Somatosensory evoked potentials (SEPs) waveform recorded from the normal and injured spinal cord in rats were analyzed. A mild compression spinal cord injury was performed in two experimental models. The first model was used to assess the disappearance and the second one the return of the electrophysiological spinal cord function after injury. In the first experimental model typical changes in waveforms morphology from normal to isoelectric line during spinal cord compression were investigated. In the second model an isoelectric line was achieved by more severe but a shorter time of compression and the typical changes in SEPs morphology after decompression were described. Our evidence suggests that the spinal cord function disappears gradually during mild compression and can return early after decompression. The amplitude after decompression first improved and then gradually deteriorated which is probably caused by secondary insult. Experimental models are both effective and simple and may be used to evaluate the effect of treatment of spinal cord injuries.