The rise of various optical clearing methods provides a great potential for imaging deep inside tissues by combining with multiple-labelling and microscopic imaging techniques. However, these methods had certain weaknesses, including toxicity of reagents, tissue deformation, fluorescence quenching, and complexity of implementation. In this study, we developed simple and rapid clearing agents for improving optical imaging depth by observing the rapid clearing process and obtaining the fluorescence images. After brain slices were immersed with sorbitol, sucrose and fructose for 1 or 2 min, respectively, the imaging depth can be enhanced rapidly with good transparency and fine fluorescence preservation for both genetically encoded green fluorescent protein and prodium iodide nuclear dye. This work provide a simple and rapid method for improving optical imaging depth.