The civil code is a unity of facts, logic and value. Both external system and internal system are descriptive concepts. In the process of legislation, the construction of external system can be relatively independent. The system benefit of the civil code is mainly reflected in the expansion of the scope of regulation, the guarantee of legal autonomy, the achievement of self-consistency and self-sufficiency, and ultimately the strengthening of the binding force and stability of law. The system benefit of civil code is more obvious in a complex society. System benefit originates from the comprehensiveness of the scope of adjustment, the hierarchical structure of the normative content and the logicality of legal meanings. The system benefit of a civil code is higher than that of separate civil laws. There are three styles of civil code: casuistry, principle and abstraction. Among them, the last one can best promote system benefit. According to the adjustment matters, a civil code should contain general clauses, clauses on fixed constitutive elements and elastic clauses, so as to maximize the efficiency of the system. As far as the external system is concerned, in the compilation of the Civil Code, China should maintain as far as possible the pure private law nature of the Code, remove from it public law clauses and unhelpful citation clauses, avoid being excessively abstract or over-specific, increase both the supply of important rules and the adaptability of the rules to new situations, adopt complete articles as far as possible, take norms of adjudication as the main body of the Code; and, if the expression of an article cannot be accurate and easy to understand at the same time, give priority to accuracy over understandability.