[Objective] The research aimed to optimize the test condition of PCR-DGGE method to analyze genetic diversity of soil microorganism. [Method] The amplified results of PCR were compared by improving high salt method for extracting soil DNA, improving primer design, changing the annealing temperature and amplification system of PCR reaction process. [Result] The result of extracting soil micro-bial DNA was better by high salt method which was improved. A single band was obtained and operation was easy when choosing 20 μl system for PCR amplification. There was no nonspecific amplification when choosing annealing temperature at 55 ℃, and cycle number of 35 was easy for following DGGE analysis. [Conclusion] The optimized PCR reaction system has high specificity and reliability.
