The application of complexity information on DNA sequence and protein in biological processes are well established in this study. Available sequences for DNMT1 gene were thoroughly explored in the information complexities. DNMT1 gene is a maintenance methyltransferase responsible for copying DNA methylation patterns to the daughter strands during DNA replication in different species. Results: We found that the entropy of DNMT1 gene in different species is DNA base composition dependent, and its complexity in mammals is lower in introns than in coding regions. We also demonstrated the impacts of entropy on domains and non-domain(s) of the DNMT1 gene. The results from DNA and protein sequences indicated that DNA evolution has a tendency toward complexity. The most interest is that the methylation’s changes of the gene over aging in a unique chick model showed aging-driven entropy characteristics, which may give an explanation of aging processes. Conclusion: In summary, the information complexity of DNMT1 gene is related to its genomic composition, which thereby associates to evolutionary and aging processing, even though the intrinsic mechanism is not to be studied yet.