| Based on geological, gravity and magnetic, seismic, logging, physical properties of rocks and testing data, the spatial variation pattern of density in Dongying sag is established. Using improved Parker arithmetic, convergence rate for model forward has been increased and stable convergence for inversion problem is ensured. Results of inversion for Pre-tertiary tectonics in Dongying sag show that: Pre-tertiary deposition in Dongying sag is controlled by NW structures. Archaean group is the crystal basement of Dongying sag, which is a north steep and south gentle rift-subsidence basin striking from NE to near EW, and the deepest position is up to -12000m at the area of Xianhe-Xinzhen. The configuration of Ordovician of lower Palaeozoic system highly inherits that of Archaean group and both have a strong consistency. The configuration of Mesozoic inherits that of lower Palaeozoic system as a whole, but filling and local reconstruction are distinct, and the scope of Dongying sag has obviously decreased. The general frame of Pre-tertiary faults in Dongying sag is a fascicular structures scattering toward NE and converging toward SW, and the north of which is two boundary faults of F1, F2 and the south is F5, F8. Pre-tertiary faults divide Dongying sag into three rift-subsidence areas of Gaoqing-Boxing, Liqin-Caoqiao and Dongying-Wangjiagang. At uplift area surrounding Dongying sag developed three igneous rock belts: Effusive rock belt of NS direction distributed along Jinjia-Gaoqing-Pingfangwang-Binzhou at west part of Dongying sag; Effusive rock belt developed along F10, F9, F8 and their intersection at south part of Dongying sag; Intrusive rock belt on Chenjiazhuang rise sporadically distributed along Lijin-Chenjiazhuang -Dongying airport. Compared with depths of penetration wells, the inversion accuracies for Mesozoic top and lower Plaeozoic top are up to 91.4% and 88.17% respectively.
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