It has been noted for decades that cancer is essentially a genomic disease. Benefiting from the latest development of high-throughput sequencing and bioinformatics technologies, a variety of genetic alterations have been identified for their roles in cancer occurrence and development, giving rise to new opportunities for anti-cancer drug discovery. In particular, the rapid advancement of cancer genomics has paved the way for the precision medicine that has gained compelling achievement in the past years and significantly benefited cancer patients. In this review, we summarize the main types of genomic abnormalities in cancer, the application of functional genomics research in cancer research, and in particular the translational application of cancer genomics in clinical diagnosis, drug discovery and cancer precision medicine. With this review, we hope to better understand cancer genomics research and provide future perspectives for its application in precision medicine.