Mitochondrial DNA (mtDNA) encodes the polypeptides required for oxidative phosphorylation and genesis of ATP. It has been though to be involved in carcinogenesis because of its high mutation rate and lacking effective repair mechanism in contrast to nuclear DNA. Since mtDNA lacks introns, it has been suggested that most mutations will occur in this coding sequence and subsequent accumulation of mutation may lead to tumor formation. Alteration in expression of mitochondrial DNA may be a general characteristic of cancer cells. The research on mtDNA such as the mitochondrial genome instability (mtGI) and the integration between the mtDNA and nuclear genome have, mainly in solid tumor, been reported recently, meanwhile it will be a critical topic in solid tumors. In this paper, we reviewed the advances in research for relationship among mitochondrial DNA mutation, abnormal expression, integration, and mtGI in solid tumors lately.