The theoretical problems about compatibility and composition of medicines in a prescription are an essential one for pharmacology of traditional Chinese medical formulae

but at present development of the theory of the compatibility delays

therefore practical further development is influenced.The author raises that the essence of a prescription is the relationship among the medicines

and regular combination of medicines is the minimal functional unit of this relationship.The combined models include both combination of medicines and combination of thinking.Prescription is composed of one to several combined units.The combination is determined by requirement of diseases

syndromes

medicines and other aspects.At the present stage

the combination should be attained by analysis of many same prescriptions and needs re-test by repeatedly practice.