The foundation of offshore wind turbines is an important factor that determines their bearing capacity and service life. A theoretical analysis and model test of the bucket foundation with and without bulkheads at a scale of 1:150 are conducted in this study. The frequency-domain impedances of the two models were obtained and compared via cyclic loading tests at different frequencies. When the loading frequency was low, the absolute values of the real and imaginary impedances of the foundation model without a bulkhead in the frequency domain were higher than those of the foundation model with a bulkhead. Based on the analysis of the variation in soil pressure at the top of the bucket, it was found that the variation in soil pressure almost alternated with the cyclic load. The adsorption force is beneficial for the bearing capacity of a composite bucket foundation, making the structure safer. The impedance matrix of the foundation is determined by the size and shape of the foundation, mechanical parameters of the foundation medium, and frequency of the forced vibration. Wolf's lumpedparameter model was evaluated for applicability to analyse the bucket foundations with bulkheads.