The as-cast CuSn10P1 copper alloy was pre-annealed and then prepared into semi-solid billets by cold rolling isothermal treatment strain-induced melting activation method (CRITSIMA). Using metallographic microscope, scanning electron microscope (SEM) equipped with energy dispersive spectrometer, X-ray diffractometer, electron probe and Brinell hardness tester, the effects of pre-annealing temperature on the microstructure evolution and mechanical properties of semi-solid copper alloy billets were studied. The results show that with the increase of the pre-annealing temperature, the average grain size of the semi-solid copper alloy billet increases, and the shape factor and liquid phase rate decrease; with the increase of the pre-annealing temperature, the solid solution in the α-Cu phase increases with more Sn element, the segregation of Sn element is weakened, the content of intergranular brittle and hard phase δ phase decreases, and the Brinell hardness gradually decreases. The existence of a new phase Cu_13.7Sn was detected in the semi-solid copper alloy billet, which is related to the high segregation of the intergranular Sn element. The semi-solid copper alloy billet prepared by pre-annealing at 600 ℃ for 2 h has fine and uniform microstructure and good mechanical properties. The average grain size is 68.34 μm, the shape factor is 0.78, the solid solubility of Sn in α-Cu matrix is 4.21wt%, and the Brinell hardness is 128 HBW.