There were many trials of cochlear prothesis, but the work on human has proceeded without firm knowledge of the stimulus coding mechanism for the normal sound stimuli. In this report, based on the electrical recordings from the cochlear single nerve fibers of cats, author presents differences between the conventional electric stimulation and the amplitude modulated electric stimulation with electrodes inserted into the scala tympani. Results were as follows : 1) The conventional electric stimulation and the amplitude modulated electric stimulation could not make differences in the tuning curves of single nerve fibers with its broad tuning and with almost the same threshold. 2) On the post-stimulus time histograms, the amplitude modulated electric stimulation made more broad spikes patterns on the time axis and more variable enveloping shapes of spikes patterns than did the conventional electric stimulation. 3) The amplitude modulated electric stimulation showed similar results with those of acoustic stimulation with regard to the latency and the enveloping shapes of spikes patterns in the post-stimulus time histograms. Based on the above results, it can be concluded that the amplitude modulated electric stimlation is superior to the conventional electric stimulation as a method of electric stimulation on the cochlear prosthesis.