CRISPR technology has rapidly changed the face of biological research, such that precise genome editing has now become routine for many labs within several years of its initial development. CRISPR/Cas9 (Clustered Regularly Interspace Short Palindromic Repeat/CRISPR-associated nuclease 9) gene editing system is a powerful and groundbreaking programmable genome editing technology developed based on an adaptive bacterial and archaea immune system resisting the invasion of exogenous nucleic acid. Compared with traditional genome editing technology, CRISPR/Cas9 system is easier, efficient and less cytotoxic. CRISPR/Cas9 gene editing technology has been applied to many aspects of cancer research, including research on tumor genes, constructing animal tumor models, screening tumor phenotypic-related and resistance-associated gene and cancer gene therapy. In this review, we focus on the application of the CRISPR screen for this fast moving field. Finally, we discuss practical aspects of screen design, and outline a further step forward in the rapidly expanding field of genome editing.