Abstract : Super-Heavy Elements (SHE) are synthesized by fusion reactions between heavy ions. Unfortunately, the fusion of very heavy systems is experimentally known to be strongly hindered, though the mechanism is not clearly understood yet. We have studied mainly the mechanism by numerical calculations, but recently have started the study with analytical method, which is supposed to clarify dynamical aspects of the physical mechanism. From where the hindrance comes, what the mechanism is, and to where the results are developed are briefly presented in the present talk.