Rapeseed is the second largest oil crop in the world, and also the most important source of edible vegetable oil in China. For a long time, rapeseed breeders have tried to breed superior varieties through traditional breeding strategies. However, Brassica napus is an allotetraploid species evolved from double diploidization after interspecific hybridization, and there are many gene redundancy in its genome. Therefore, the efficiency of improving traits through traditional genetic methods such as artificial hybridization selection and random mutagenesis is very low. To achieve rapid and efficient innovation of germplasm resources and genetic improvement in rapeseed, the application of CRISPR/Cas9 gene editing technology is not only appropriate but also timely for rapeseed. In recent years, CRISPR/Cas9 technology has been widely used in gene function research and targeted genetic improvement of polyploid rapeseed due to its unique advantages of high efficiency and simplicity. The present article reviews the current researches on the application of CRISPR/Cas9 system in the study of gene function and genetic improvement of rapeseed, involving important agronomic traits such as yield, oil content and fatty acid composition, biological and abiotic stress tolerance. The limitations of gene editing in rapeseed and the direction of its future development were also discussed.