The plate-monopile hybrid foundation, owing to its structural simplicity, cost-effectiveness, and potential for life extension, has emerged as a promising alternative to monopile in complex marine environments. However, its mechanical performance and soil-structure interaction mechanisms under unidirectional cyclic loading remain insufficiently investigated. In this study, the Walney Wind Farm is as a test site, FE models of monopile and plate-monopile hybrid foundation are established to comparatively analyse the mechanical responses under fully recovered and partially recovered unidirectional cyclic loading, to evaluate the improvements in performance of the hybrid foundation, and to elucidate the soil-pile interaction mechanisms. The results indicate that: (1) The hybrid foundation reduces the accumulation of peak and residual deflection, with distinct evolution patterns under fully recovered and partially recovered unidirectional cyclic loading. (2) Unloading stiffness of the hybrid foundation exceeds that of monopile and resists degradation more effectively, particularly at higher loading amplitudes. (3) Stress distribution beneath the plate and around the pile shows clear double-peak features under fully recovered unidirectional loading, which diminish or evolve into single-peak distributions under partially recovered unidirectional loading. (4) The hybrid foundation suppresses the accumulation of bending moment more effectively than shear force.