Event-related brain potentials (ERPs) were recorded to explore the electrophysiological correlates of breaking mental set when subjects performed the Chinese character-generation task. A new experimental paradigm (learning-testing model) was adopted in order to make subjects find a solution actively by using a fixed way (Rep: repetition) or a new method (BMS: breaking mental set). Results showed that BMS elicited a more positive ERP deflection (P500-700) than did Rep between 500 and 700 ms after onset of the test stimuli. The P500-700 was possibly involved in the successful breaking of mental set and the initial forming of new associations during problem solving. Furthermore, BMS also elicited a more positive ERP deflection (P900-1300) than did Rep between 900 and 1,300 ms. The P900-1300 might reflect searching and generating a new character after breaking mental set.