Abstract: In the formal legal reasoning, it is only through judgement of value that we can open the logical access to premise and condasinon, avoiding making mistakes or middle-term inconsistency; and essential justice judgement or value has the functions of discovery, comparison, selection, classification, narur-determining, verdict, which are indispensable to legal reasoning. There is no legal reasoning without judgement of value. Where there is judgment of value there is legal reasoning. So judgement of value is soul of legal reasoning.