In this paper, using the division of plate tectonics for reference, we have discussed that the Orduoce Block may be an independent block based on some facts of geology and seismology. And by the stress field from the solution of earthquake source mechanism and distribution of water-system etc. we have shown counterclockwise torsion in this block, which is used to discuss the regional seismicity. When comparing the movement of the block with the torsion of the cylinder of elliptic section, we found theoretical pattern of symmetric rise-sinking will show no difference from the pattern of tectonic motion of the block in Quaternary period. We have analysed symmetric echo of seismic activity of block boundary, mechanical character of the area of occurring great earthquake, the distribution of great earthquake along block boundary, the collusion of boundary fault from the earthquake and mechanical preperties of the fault etc. by the result obtained from the study of cylinder torsion of elliptic section. On this basis, we put forward five respects which are needful to estimate the trend of earthquake of block region. Then, shortrange trend is estimated.
After the preliminary analysis of force source we consider that Pacific plate play a main part in the movement of the Orduoce block, but the reflection of Indian Ocean plate can't overlooked too in it.