Objective To explore a fast, effective and noninvasive method of genomic DNA extraction. Methods We compared the genomic DNAs extracted by two DNA extraction methods of potassium iodide (KI) and Kit from saliva (fresh and placed a week at room temperature), and PCR amplifications were done for TP53 and PRB-3 genes from their extracted DNA. Ninety-nine healthy children and adults were recruited and their saliva samples were collected to detect the stability of DNA extracted by KI. Results High quality genomic DNAs were extracted by both methods from the fresh saliva. The DNA yield based on KI was (1.91±0.15) μg, with the D₂₆₀/D₂₈₀ being 1.99±0.05, and that of Kit was (2.64±0.34) μg, with the D₂₆₀/D₂₈₀ being 1.81±0.02. Although the extracted DNAs had obvious degradation from saliva samples placed for a week at room temperature, the expectant DNA fragments were successfully amplified by PCR for TP53 and PRB-3 genes using these extracted DNAs. Although the genomic DNAs from saliva samples of 99 healthy volunteers by the method of KI showed individual difference (DNA yield was [1.89±0.46] μg), the DNA quality was stable and reliable (D₂₆₀/D₂₈₀ was 1.96±0.10). Conclusion KI method for extracting genomic DNA from saliva is not only cheap and highly effective, but also noninvasive, making it suitable for large-scale epidemiological studies.