Rapeseed is the second largest oil crop in the world and the most important source of edible vegetable oil in China. Rapeseed breeders have attempted to breed elite varieties through traditional breeding schemes for a long time. However， Brassica napus L. is an allotetraploid species that evolved from double diploidization after interspecific hybridization， and there is a significant amount of gene redundancy in its genome. Therefore， the efficiency of improving traits through traditional genetic methods including artificial hybridization selection and random mutagenesis is very low. In recent years， CRISPR/Cas9 technology has been widely used in studying gene function and targeted genetic improvement of polyploid rapeseed due to its unique advantages of high efficiency and simplicity. It is timely to apply CRISPR/Cas9 gene editing technology to Brassica napus L. for the rapid and efficient innovation of germplasm resource and genetic improvement. This article reviewed the progress towards the application of CRISPR/Cas9 system in studying gene function and genetic improvement of rapeseed， involving important agronomic traits such as yield， the content of oil， the composition of fatty acid， the tolerance of biological and abiotic stress. The limitations of gene editing in rapeseed and the directions for future development were discussed as well.