5at%Yb∶CaF2 nano powders were synthesized by the co-precipitation method. The powder is pure cubic CaF2 phase and the average particle size was about 45 nm. Meanwhile, the Yb∶CaF2 nano powders are well-distributed and the shape of small particles is close to cubic. 5at%Yb∶CaF2 transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) post-treatment. The influences of vacuum pre-sintering temperature on the phase, densification, microstructure and optical transmission of the ceramics were studied. The results show that all the ceramics pre-sintered in vacuum at different temperatures are still pure cubic phase. After HIP post-treatment, 5at%Yb∶CaF2 ceramics with the thickness of 3 mm pre-sintered at 650 ℃ under vacuum have the best optical quality and the in-line transmittance reaches 87% at 1 200 nm.