A simple process is demonstrated to transfer the self-assembly of submicrospheres from solid substrate to liquid surface in fabricating synthetic opal. Irradiating light and controlled airflow are used to control the evaporation of solvent. This process induces solid layer with colors. SEM images of the solid layers show that those layers are synthetic opals for well ordered polystyrene spheres in a hexagonal close-packed structure over a large scale. An absorption peak is also observed at 541 nm in normal transmission spectrum of the fabricated sample. Furthermore, investigation of the phase transitions indicates that nuclei of synthetic opals grow up through accumulating at their bottom and extending at their edges during self-assembly.