Abstract . A draft of the whole human genomic sequence has been completed and published in 2001. Researches on structural genomics, functional genomics, proteomics, evolutionary and medical sciences have just begun since. The existence of ninety percent repetitive, non-coding sequences in the human genome and in other mammalian species as well, indicating some potential but unaware functions of these repetitive regions within the mammalian genomes remained to be discovered. Among all features in the genomic sequences, microsatellite has been characterized as one type of short tandem repeats (STRs), abundant in the human genome, which potentially plays some important roles in biological processes, such as makers for molecular biology, the enhancers for transcription, and protein-binding sites. Changes on microsatellite copy numbers also involve in the cause of a couple of diseases have been reported. The sequence of human chromosome 20 has been finished in Dec. 2001, which provided us a valuable resource to study about gene density and the distribution of repetitive sequences such as microsatellties as well. To build a more detail chromosome 20 microsatellite map, including di-, tri- and tetra-nucleotide microsatellites, we therefore designed a sequence-based, molecular markers discovery system by bioinformatics approaches. The results indicate that these repetitive sequences distribute across the chromosome 20 evenly. We further analyzed the GC content of the human chromosome 20. A comparison of GC content, microsatellite distribution and gene density of each contig shows some correlation among them. The slippage rates of di-nucleotide microsatellite were predicted by the formula basing on Markov Chain. Some interesting results were found in this thesis. The same approaches were applied on human chromosome 14, which was being completed sequencing in Feb. 2003. The results implied that our strategies might be useful in the advanced genetic studied or medicine researches.