Introduction: DNA extraction from the ancient bones tissues is currently very difficult. Phenol chloroform silica method is one of the methods currently used for this aim. The purpose of this study was to optimize the assessment method.Methods: DNA of 62 bone tissues (average 3-11 years) was first extracted with phenol chloroform silica methods and then with changing of some parameters of the methods the extracted DNA was amplified in eight polymorphisms area including FES, F13, D13S317, D16, D5S818, vWA and CD4. Results from samples gained by two methods were compared in acrylamide gel.Results: The average of PCR yield for new method and common method in eight polymorphism regions was 75%, 78%, 81%, 76%, 85%, 71%, 89%, 86% and 64%, 39%, 70%, 49%, 68%, 76%, 71% and 28% respectively. The average of DNA in optimized (in 35l silica density) and common method were 267.5 μg/ml with 1.12 purity and 192.76 g/ml with 0.84 purity respectively.Conclusions: According to the findings of this study, it is estimated that longer EDTA attendance is an efficient agent in removing calcium and also adequate density of silica particles can be efficient in removal of PCR inhibitors.