在计算理论中，幂集构造是转换非确定有限状态自动机（NFA）到识别同样语言的确定有限状态自动机（DFA）的标准方法。它在理论上的重要性源于它确立了NFA尽管有额外的灵活性，它不能识别不能被任何DFA识别的任何语言。在实践中的重要性源于它把易于构造的NFA转换成了更有效执行的DFA。但是如果NFA有n个状态，结果的DFA可能有最多2个状态，这种指数增长有时使这种构造对于大NFA而言是不实际的。

In the theory of computation and automata theory, the powerset construction or subset construction is a standard method for converting a nondeterministic finite automaton (NFA) into a deterministic finite automaton (DFA) which recognizes the same formal language. It is important in theory because it establishes that NFAs, despite their additional flexibility, are unable to recognize any language that cannot be recognized by some DFA. It is also important in practice for converting easier-to-construct NFAs into more efficiently executable DFAs. However, if the NFA has n states, the resulting DFA may have up to 2 states, an exponentially larger number, which sometimes makes the construction impractical for large NFAs.