Reaction wood formation and reorientation process of growth axis is heterogeneous from the normal wood at the point of activities of cambium region. The structural changes of cell wall level initiate formation of reaction wood(RW) and effect its behavior to reveal the variety of properties. In leaning stem, compression wood(CW) is developed in lower side but tension wood(TW) is formed on the upper side. The cell walls of CW are thicker than those in normal wood and contain more lignin but less celluose and lack S3 layer. In TW, cellulose consist of the thick, inner cell wall G-layer but nearly lacking lignin. And various 6 patterns of 2nd cell wall structure in wood fiber, are the distinction for identification and evolution of the angiosperm species. The outstanding characteristics of cross section is eccentrical annual rings with extraordinary increment wide colored darker than the opposite side, but the increase of early wood in eccentric rings can be regarded as the normal growth photo-tropically without RW. The formation of RW can also be effected by environment, internal factor and plant hormone. Finally, analogy to understand RW(CW, TW) can be to design 2 modes of bridge construction or 2 transductive styles of driving power in motor engine, in the way of force direction of pushing or pulling..