There are one or more erosion surfaces in oil-bearing basins. Study on the relationship of erosion surface and reservoirs could not only develop oil theory, but also could promote exploration in the eastern old oil-bearing areas of China. In this paper, a space-time relationship of oil-bearing strata and erosion surface has been established based on the statistic analysis of erosion times and quantities in oil-bearing basins and the contribution of strata rift and erosion to oil accumulation has been discussed in terms of oil accumulation mechanism by geological analysis. The statistic and geological analysis showed that the strata eroded or the strata below the erosion surface are oil-bearing beds; the time of strata rift is coincident with the time of oil accumulation; the fall of fluid temperature and the rebound of the pore during the process of strata rift and erosion will cause underpressure in the strata which pumps oil and gas in the reservoirs, especially, the rebound of the pore offers extra-space to oil and gas accumulation.