A series of phenyl polysiloxane-modified polyurea/ polyurethanes (SPUs) with different silicone loadings (10,20,30, and 40 wt %) have been designed and synthesized. The structures of SPUs were confirmed by 1 H NMR, 13C NMR, and FT-IR. The impact of phenyl polysiloxane content on the properties of SPUs was fully studied. The residual methoxy groups on silicon could help SPUs form interpenetrating networks accompanying with the residual isocyanate under moisture, which was different with the conventional moisturecrosslinking polyurethane system. The properties of SPUs films have been fully researched by attenuated total reflection flourier transformed infrared spectroscopy, thermal analysis, tensile tests, water contact angle, X-ray photoelectron spectroscopy, SEM, and AFM. Results indicated that the introduction of phenyl polysiloxane improved the thermal stability and remarkably increased the water contact angles accompanying with a comparable mechanical strength to the pure polyurethane. Meanwhile, it also brought out the decreased microphase separation and water absorption. The obvious surface migration has been observed in the SPUs, which changed their surface properties. Some voids were observed in all moisture curing SPUs system, but the phenyl silicone content impacted on the numbers and sizes of the voids. The phenyl groups introduced and carbon dioxide produced in the crosslinking procedure helped to form and stabilize the voids in the SPUs.