Abstract: The petrology and zircon ages of the Ordovician sandstones in northern Sonid Left Banner area of Inner Mongolia were studied in this paper. The sandstones belong to a kind of lithic sandstone with lots of volcanic debris. The sandstone grain matrix component diagrams show that the sandstones came from the recycled orogenic belts. LA-ICP-MS dating technique was used to make detrital zircon analysis for one sandstone sample, and the age periods obtained are from low to high as follows: ①440~574Ma with the major peak at 506Ma and subordinate peak at 442Ma; ②650~799Ma with the peak at 767Ma; ③874~936Ma with the peak at 887Ma; ages of the other four zircon samples are 1145Ma, 1756Ma, 2618Ma and 2626Ma, respectively. Based on the comparison of ages and magmatic events with relative adjacent cratons and/or terrenes, the authors infer that the sandstones formed at 440Ma, and the provenances were mainly derived from the Erguna and Xing'an terranes, with the sedimentary process affected by volcanic events.