When investors in the financial market have highly correlated descision, there is a higher probability to trigger systemic risks by herd effect. This study uses principal component analysis to produce the first principal component explains and change of the first principal component explains, and uses the two indicators to predict systemic risk events that have fallen by more than 20% since 2005. The study found that indicators can predict systemic risks, and both indicators have better predictive ability compared with the TAIEX Options Volatility Index.