Abstract: With the continuous improvement of drilling and completion technology and the requirement for development of geological reservoirs, horizontal wells are widely used in Bohai oilfield. When drilling horizontal wells in reservoirs with bottom water and edge water, the key is the drilling of landing section in horizontal well, that is, the key is the process to find oil. The deepening or shallowing of reservoir not only affects the research decision of oil-water interface in geological reservoir, but also affects the normal drilling and cost of landing time of horizontal well. The prediction accuracy of horizontal well landing depth is mainly geological factors and drilling factors. In this paper, starting from the error of drilling engineering system, the cause of landing error has been analyzed, and the measures to decrease landing error have been put forward, which can provide the basis for the prediction of the depth of the subsequent adjustment wells.