Abstract The Chengbei fault slope of Huanghua Depression lies in the slope belt between the Qikou Sag and the Chengning Uplift, and develops many unconformities. These unconformities are very important for the hydrocarbon accumulation in this area. By analyses of seismic data, the unconformity can be divided into fold unconformity distributing in the basement, faulted-fold unconformity distributing in the downthrown block of the large rift, truncation unconformity distributing in the upthrown block, onlap unconformity distributing in the slope area of the uplift and parallel unconformity distributing in the sagging area. According to the log data, the unconformities are divided into three parts vertically: rocks developed above the uncoformity, weathered clay layer and semi-weathered clay layer. Because of the differences in thickness and lithology, the vertical textures of unconformity include four patterns of lithology configuration, namely ACE, ADE, BCE and BDF. The unconformities in the Chengbei fault slope are not only the important paths for the oil and gas lateral migration, but also the good places for the petroleum accumulation. Onlap unconformity petroleum reservoirs can be formed above the unconformity, and truncation unconformity petroleum reservoirs can be formed below the unconformity due to the weathered clay layer. The exploration has proved that a lot of petroleum display and petroleum reservoirs are deposited in the 50 m range above and below the unconformities. The researches of relationship between unconformity and petroleum accumulation will broaden the exploration area of subtle reservoirs in the Huanghua Depression and have important academic and practical significances for the further exploration in eastern China basins.