Objectives : The objectives of this study is to establish data-base to find out similar herbal formulas with a particular herbal formula by comparing composition ratio of configuring herbs. And this thesis is to analyze differences of prescriptions and find out similar prescriptions by utilizing galenical mass ratio, which is directly related to effectiveness of galenical. Methods : This study was proceeded by using Access 2007 with Window 7(MS) and 2,787 prescriptions of which herbal configuration could be indicated by weight unit were analysed from Donguibogam. We standardize all units of the prescription and input the mass ratio data when entered galenical data. Results : We could confirm a degree of similarity between compared prescriptions and a particular prescription according to the sum of differences of herb weight ratio and similarity ratio. Conclusions : A most similar herbal formula could be searched through comparing multi prescriptions by multi prescriptions of herbal configuration from established herbal formula data-base where herb weight ratio of prescriptions is to be input.