Abstract: An offshore wind generator usually adopts a high-level concrete platform supported on cylinder piles. Thus, a tidal hydrodynamic force may result in the vibration of the high structure of a generator-tower foundation, and threaten its security. This article studies tidal flow fluctuating pressure properties of an eight-cylinder-pile group foundation through a hydraulic model test. The results show that the fluctuating pressure can be regarded as a stationary random process; the time domain amplitude characteristics display many differences with a single cylinder; in frequency domain, the energy characteristics reveal the major frequency of flow fluctuating and the vortex shedding frequency.