Objective To construct DNA library ,genomic DNA was extracted from Tyzzer organism. Methods Three methods (density gradient centrifugation combining enzymatic digestion method, enzymatic digestion method, and filtration salting-out combining centrifugation method) were used to purify Tyzzer organism from infectious livers, and results of purification were compared. Genomic DNA was extracted from Tyzzer organism by three methods (benzyl chloride-method, kit and phenol method), character of which was analyzed. Results Tyzzer organism was purified effectively by filtration salting-out combining centrifugation method. Genomic DNA extracted by phenol method was high quality and specificity.Conclusion Genomic DNA was first extracted from Tyzzer organism successfully, which can apply to many experiments of molecular biology.