During the past few years, although scientists and researchers have studied variations in the cancer genomes, our current knowledge about the function of Micro-inversions (MIs) in cancer are still limited. MIs are generally defined as small inversions in DNA segments shorter than 100 bp. To expand our knowledge of their roles in cancer, we analyzed the MIs of 209 samples from four types of cancer, including hepatocellular carcinoma, lung cancer, pancreatic cancer, and bladder cancer. Within all the 209 samples, we identified 2,925 MIs, of which 1,519 (51.93%) are in gene regions. Of the 1,519 MIs in the gene regions, 106 (6.98%) are in the exon regions. We also analyzed 209 healthy samples as the control samples. We further analyzed the distribution of MIs in the four types of cancer among 24 chromosomes. Besides the chromosome preference, different cancers also have different preference for various genes. The MIs preference for different genes among four types of cancer may provide a guidance for the treatment and diagnosis on the four types of cancer. Medical doctors should concentrate more on chromosomes and the genes that MIs prefer to locate on. We also calculated the average count of MIs per individual among each cancer. From this result, we found that the bladder cancer has the most average count of MIs per individual, which means MIs may be more likely to exist in bladder cancer. According to our analysis, MIs play an important role in cancer and should be considered for further analysis.