After the nerve selective regeneration theory was put forth [1], many researchers had focused on it and its possible application. According to our previous study, the results of small gap sleeve bridging peripheral nerve mutilation had been confirmed [2]. But the imminent causes of those results haven't been unveiled completely. This study tries to explore these reasons in some aspects. The results indicate the advantages of this new surgical method not only because of nerve selective regeneration but also because the small gap can create a suitable microenvironment for peripheral nerve regeneration.