Herein, we report a facile surfactant-assisted solvothermal synthetic method to prepare nearly monodisperse spherical CeO2 nanocrystals. A good control of the size of CeO2 nanocrystals in the range of 100–500 nm was achieved by simply varying the synthetic parameters such as reaction time, volume ratio of ethanol to water (R), molar ratio of PVP, and concentration of Ce(NO3)3⋅6 H2O in solution. A possible mechanism for the growth of spherical CeO2 nanocrystals is proposed. The obtained CeO2 nanocrystals with a surface area of up to 47 m2g−1 were then employed as a catalyst support. By loading Au-Pd nanoparticles (about 3 wt. %) onto the CeO2 support, an Au-Pd/CeO2 catalyst was prepared that exhibited high catalytic activity for HCHO oxidation. At the low temperature of 50 °C, the percentage of HCHO conversion was 100 %, suggesting potential applications in preferential oxidation and other catalytic reactions. These Au-Pd/CeO2 catalysts may also find applications in indoor formaldehyde decontamination and industrial catalysis. The facile solvothermal method can be extended to the preparation of other metal oxide nanocrystals and provides guidance for size- and morphology-controlled synthesis.