A graph-based natural language optimization method and an electronic apparatus are provided. The method is adapted for an electronic apparatus with a processor. In the method, an input sentence submitted by a user is received, and multiple domain-related entities are extracted from the input sentence. The domain-related entities are input to a graph database to analyze a connection relationship between the domain-related entities, and filling data is obtained from the graph database based on the connection relationship. The input sentence and the filling data are integrated via a natural language processing technology to generate an optimized natural language sentence.