In the development process of edge and bottom water reservoirs and low permeability reservoirs, there are some problems such as great production pressure drop, low single well productivity, and low utilization degree. In order to solve the difficulties of such reservoir development, horizontal wells have been applied to the oil and gas production in Xihu oil and gas field, East China Sea since 2006. At present, the efficient development of horizontal wells has been proven by actual production of multiple oil and gas fields. The production pressure difference of the strong edge and bottom water gas reservoirs is only 0.4 MPa when the horizontal well is used for production. The dry period is extended for 2 years and the production is maintained. After multi-branch horizontal wells are used in low permeability gas reservoirs, the open flow capacity is 3～5 times higher than that of vertical wells, and the average annual decline rate of multi-branch horizontal wells in 6 years is only 6.7%. The successful application of horizontal wells in Xihu oil and gas field, East China Sea has brought great economic benefits of offshore oil and gas field development, and also provided guidance for the selection of well types for subsequent oil and gas reservoir exploitation.