Abstract: Hydraulic conductivity is an important parameter describing groundwater movement in the groundwater diffusion equation. The traditional method is to give a disturbance to the groundwater system by pumping or injecting water, monitor the response of groundwater levels to the tide, and calculate the hydraulic conductivity of an aquifer. In this paper, a method of tidal attenuation rate is proposed to identify the hydraulic conductivity. It is suitable for identifying parameters of a confined aquifer in coastal areas. After deriving the analytical solution, the hydraulic conductivity of the aquifer is obtained by numerical fitting, least square method and Newton iteration method. The concept of tidal attenuation rate is proposed. The linear relationship between the cotangent function and the tidal attenuation rate is established. The slope and intercept of the linear relationship are used to identify the hydraulic conductivity. In this paper, the hydraulic conductivity identified by the method of tidal attenuation rate is equal to its actual value, showing that the method is correct and effective. The attenuation rate of tidal signals is linearly correlated with the cotangent function of sea water oscillation. The numerical simulation shows that the method can accurately estimate the hydraulic conductivity of the aquifer. The method of tidal attenuation rate has the advantages of less well-drilling, being economical and efficient. The tidal attenuation rate method provides a reliable theoretical basis for practical engineering applications and can be used in some practical projects. The limitation of this method lies in the need of some parameters of the aquifer, such as the length of the aquifer, the amplitude and frequency of sea water fluctuation, etc.