Abstract: In this paper, the authors collect and analyse all available data from oil wells in the Bohai Bay Oil Fields before and after the Tangshan Earthquake from 1970 to 1980. They show certain anomalous phenomena as follows:(1) The data reveal that the oil production in wells is apparently influenced by the development and occurrence of earthquakes.(2) The anomalous variations consist mainly in the quantity of oil production and pressure in wells before the Tangshan Earthquake.(3) The curve of pressure variation measured at the casing head is similar to that by the method of hydraulic fracturing before and after fracturing of rocks.(4) The anomalous variations before the Tangshan Earthquake in natural oil producing wells, not yet influenced by man-made effects, show rather clearly. But such wells are very few in number and sooner or later will be turned to artificially driven ones, and become complicated.