In a process of constituting a legal act, when one party who negligently causes impairers to the other party, this can been seen as a fault in legal act-making; Its thus should take the undertakes an obligation of compensation, and which is called the liability of pre-legal act. Regarding a jurisprudence topic construction, our hierarchy of civil law is substantially relies on the legal development path of German and Japanese law, which adopts the approach of liability for fault in contract-making. And in this foundation, the revision of the Obligation part of the ROC Civil Code (a Art.245-1 revising and Art.247 revision), completes the concrete legislation establishment, takes the liability for fault in contract-making as the main system of the liability of pre-legal act, determined for it, turns round affirmed for the mainstream scientific theory. The liability of pre-legal act, concludes a liability for fault in contract-making, should face other pre-legal act reforming to the questions of the liability for fault in contract-making, its solution, inevitable, must widely cite the analogy to be suitable, the formation "liability of pre-legal act = liability for fault in contract-making type article + analogy is suitable" the system essence. A set of legal theory, must widely be suitable with the aid of the analogy, can fill the continually loophole reluctantly, whether completely symbol system rigorous integrity examination? If the legal solution has feasible replacements when it is to apply, whether could attempt the exploration and the appraisal? Should be the important topic is worth exploring. The legal system constitution in liability of pre-legal act, the ROC Civil Code Art.113 is a special article which is equipped with German and Japanese civil law not to have; if is not rash denies Civil Code Art. 113 the standard function, then it manifests the substantive content, the scientific theory want to construct the liability of pre-legal act, quite tallies. It and so on has compared with civil law mainstream ideological mode attribute's one of 245th, resembles can draw close the case the objective special details, by elastic mechanism strengthening rights and interests protection and specifically just realization properly. As the Civil Code Art.113, if it doesn't limit the range of the compensation to the protection of the reliance interest, it can expand the system mode that from the compensation of reliable interest to performance-interest theoretically. Deriving this contention not only close to most of the foreign countries but accords with the later cogent civil-law theories of Germany and Japan. Furthermore, the rehabilitation of the Civil Code Art.113 can be the reason of the compensation of Unjust Enrichment; Because, does not pay when profits the benefit returns the scope, should take reply (before rights and interests change) the original condition as to be suitable the criterion, but must supposes is restricted in the extant benefit. Moreover, the Civil Code Art.113 about the reply original condition stipulation, is following by the Dali Court (the same as Judicial Yuan) early time in the legal precedent, its legislation has custom-made, and not comes from no legal jurisprudence or comes suddenly. Because of the statement, the article focuses on Civil Code Art.113. On one hand, I observe and sum up legal-history and development of comparative law. On the other hand, according the Legislative Yuan and the interpretation, I will concern the important questions about a fault in legal act-making. The following are its relevant key points which about construct a system for a fault in legal act-making, and which hope to construct a complete system of the liability of pre-legal act for the ROC Civil Code and broach some suggestions.