Semi-solid rheological squeeze forming has distinct advantages over traditional casting and forming techniques. In this study, a high-performance thin-walled CuSn10P1 alloy was successfully produced by combining liquid-metal instantaneous undercooling-induced nucleation, semi-solid slurry homogenization treatment, and semi-solid rheological squeeze forming. The effects of the forming specific pressure (MPa) and filling speed (mm/s) on the microstructure and mechanical properties of these parts were explored in this study, and the influence of the intergranular brittle phase (α-Cu + δ-Cu41Sn11 + Cu3P) content on the mechanical characteristics was determined. CuSn10P1 alloy with a Cu13.7Sn phase exhibiting a large number of spherical or nearly spherical morphological features coexisting with the high-tin solid-solution layer morphology was discovered and prepared at a mold temperature of 485 °C, specific pressure of 165 MPa, and filling speed of 22 mm/s. Parts with this microstructure had excellent mechanical properties, including an ultimate tensile strength of 419.95 MPa, yield strength of 228.89 MPa, and an elongation of 13.71%. This study illustrates the viability of semi-solid rheological squeeze casting for manufacturing high-performance thin-walled high-tin copper alloys. [ABSTRACT FROM AUTHOR]