This paper investigates the influence of the composite index of investor sentiment on the timevaryinglong-term correlation of the U.S. stock and bond markets based on the DCC-MIDASmodel. We modify the model by considering structural break points of the 1997 Asian financialcrisis and the 2008 global financial crisis based on the Bai and Perron (2003) test to adjust thecorrelation during different periods. The results show that the composite index of investor sentimenthas a significantly positive influence on the long-term stock-bond correlation, and theshock of crises significantly decrease the average correlation but the effect of sentiment does notchange significantly. Finally, our out-of-sample analysis presents significant improvement for theperformance of portfolio allocation after involving the effect of investor sentiment on the longtermstock-bond correlation.