To meet the requirements of the multi-phase flow water holdup measurement at the surface wellhead of oil production, a permanently dynamic and static water holdup measuring device for surface wellhead (PDSWHMD_SM) is designed and developed by combining dynamic conductance measurement and cylinder capacitance static measurement techniques. This article establishes a numerical model of the permanent conductance-capacitance integrated sensor (CCIS) using the finite element method (FEM). And the medium distribution characteristics of the fluid flow and stationary state in the pipe, CCIS structural parameters, electric field distribution, and response characteristics have been studied in depth. The optimal structure parameters of CCIS are finally determined: He = 90 mm, ID= 30 mm, Ihe = 3 mm, Hc = 375 mm, IR1 = 26 mm, Tc = 1 mm, Hm = 56 mm, which are proved to be within 5% of the measurement error. In addition, this article conducts an experimental study with multi-phase flow conditions such as the total flow rate range of 5~ 70 m 3 / d and the water holdup range of 50% ~ 90% . The results show that the developed device PDSWHMD_SM has good water holdup measurement performance with the error of water holdup measurement within 5% . Both simulation and experiment demonstrate that PDSWHMD_SM performs well in water holdup measurement.