The writer summarizes the biological behavior of Mitochondrial DNA deleted cells (ρ0 cells) of multiple tumor cells to investigate the effects of mitochondrial DNA (mtDNA) deletion on tumor. Apoptosis, growth and invasion ability of tumor cells can be affected by mtDNA deletion. It can also induce the multidrugresistance phenotype of tumor cells. MtDNA deletion mainly affects the tumor in two aspects: energy metabolism and intracellular signal transduction. This study may lead to the development of anti-cancer drugs targeting mtDNA.