Abstract: Although there exist many doubts on defining the relative concepts of juristic act in General Provisions of the Civil Law, the definition of juristic act's concept in it accords with law's scientific logic, based on the concept created for juristic act to function as realizing the autonomy of private law. In another words, the key meaning of juristic act is to endow human will with legitimization and peremptory sanction. It is legal will declaration. Will declaration is the expression of wills by the legal personality, which possesses legal effect and purpose. Based on the contract juristic act's nature and its reliable characteristic, the definition of contract's concept in Contract Law also accords with law's scientific logic; that is, the contract is legal act of setting civil rights and responsibilities.