The article has made a simple exposition of the dilation-creep modelof earthquake source development(abbreviated DC).Inelastic volumetricdilation of rock masses and fault creep are considered as two basic phys-ical processes in the DC model.The physical mechanism of precursors ofthe M=7.8 Tangshan earthquake has also been analysed and discussed inthis paper.The results show that the precursors of the Tangshan earth-quake were not caused by only one factor and the precursors observed in-and around the epicentral area prior to this earthquake can be grouped into three types.TypeⅠprecursors may be causally related to rock dilata-ncy.TypeⅡprecursors result from fault creep.TypeⅢprecursors maybe associated with some sort of upward migration of mass in the crust orthe upper mantle,and/or may be attributed to large scale stressing processaccommodated by some combination of stable slippage and discontinuousbrittle rupture(namely small earthquake)along the faults.It was sug-gested that repeated dilation and discontinuous creep occurred during theprocess of source development of the Tangshan earthquake and the prepa-ratory process of the Tangshan earthquake can be divided into the follo-wing six phases:elastic stress accumulation(from 1954 to 1967);earlyinelastic dilation(from 1968 to 1969);early fault creep(from 1970 to1973);the second dilation(from the end of 1973 to the first half of 1975);the second evident fault creep(from the second half of 1975 to the end ofApr.1976);and fault creep just before the main shock(from the end ofApr.1976 to the occurrence of the Tangshan earthquake).It is regardedhat the preparatory process of the Tangshan earthquake,as one of the intraplate events,may be controlled jointly by the upward migration ofdeep mass and large scale intraplate stress field.This characteristic prob-ably is different from that of earthquake along plate boundary. The article has made a simple exposition of the dilation-creep model of earthquake source development (abbreviated DC). Inelastic volumetricdilation of rock masses and fault creep are considered as two basic phys-ical processes in the DC model. The physical mechanism of precursors of the M = 7.8 Tangshan earthquake has also been beensed and discussed inthis paper.The results show that the precursors of the Tangshan earth-quake were not caused by only one factor and the precursors observed in-and around the epicentral area prior to this earthquake can be grouped into three types .ype Ⅰprecursors may be causally related to rock dilata-ncy.TypeⅡprecursors result from fault creep.TypeⅢprecursors maybe associated with some sort of upward migration of mass in the crust orthe upper mantle, and / or may be attributed to large scale stressing processaccommodated by some combination of stable slippage and discontinuousbrittle rupture (on small earthquake) along the faults.It was sug-gested that re peated dilation and discontinuous creep occurred during the process of source development of the Tangshan earthquake and the prepa-ratory process of the Tangshan earthquake can be divided into the follo-wing six phases: elastic stress accumulation (from 1954 to 1967); earlyinelastic dilation (from 1968 to 1969); early fault creep (from 1970 to 1973); the second dilation (from the end of 1973 to the first half of 1975); the second evident fault creep (from the second half of 1975 to the end of Apr. 1976) ; and fault creep just before the main shock (from the end of Apr. 1976 to the occurrence of the Tangshan earthquake). It is assumed that the preparatory process of the Tangshan earthquake, as one of the intraplate events, may be controlled jointly by the upward migration ofdeep mass and large scale intraplate stress field.This characteristic prob-ably is different from that of earthquake along plate boundary.