陕西渭北煤田主采石炭、二叠系煤层，煤系基底为中、上奥陶统厚层石灰岩，本文利用大量实际资料证明：煤层中的小构造主要是由基底起伏所引起。而且根据基底起伏程度和起伏方式得出其对煤层构造具有不同的影响规律，为合理有效地选择采煤方式提供了可靠依据。 The main coal-bearing strata of Carboniferous and Permian in Weibei coalfield in Shaanxi Province are thicker limestone of middle and upper Ordovician. The paper uses lots of practical data to prove that the small structure in coal seam is mainly caused by the basement undulation. And according to the extent of the basement undulation, it is concluded that it has a different influence on the coal seam structure and provides a reliable basis for choosing the coal mining mode reasonably and effectively.