Abstract: The intraplate earthquakes and the interplate earthquakes are quite different in depth of seismic foci, mechanism and other characteristics. From this consideration, China and its adjacent regions may be divided into the Marginal Pacific Seismic Domain and the Tethys-Himalayan Seismic Domain, both of them subdivided into inner belt and outer belt respectively. The two domains act upon each other to make up an "intervening belt", i. e. the North-South Seismic Belt.Basing upon the statistical analyses of accumulative energy released from strong earthquakes (M≥6-7) in China and the adjacent regions during 1904-1977, it is demonstrated that seismic activity of inner belt is in its higher level when seismic activity of outer belt is in its lower level and vice versa. This kind of phenomena can also be referred as "shielding" of seismic belt. The function of shielding may be better or worse in different sections of inner seismic belt to permit seismic activity weaker or stronger in the corresponding sections of outer seismic belt. For example, shielding in Nakha-Arakan Yoma-Andaman is better than in the Himalayas, so that seismic activity is weaker in the western Yunnan and the Indochinese Peninsula than in the Qinghai-Xizang Plateau. Likewise, Taiwan, Northeast Japan and Chishima shield better than Ryukyu and Southwest Japan do, therefore seismic activity is weaker in South China and Northeast than in North China.Intraplate earthquakes may primarily be attributed to strengthening horizontal stress resulting from the interaction between plates on the margins. The other causes such as ascenting plume, mantle uplifting, earth-tide,Chandler wobble and variation of rotation velocity of the earth might be of the secondary importance.