In order to study the cross correlation between the volatility of stock market and online financial news emotional intensity, this paper firstly establishes the emotional dictionary and conducts research on the sentiment analysis method about online financial news. Secondly, it investigates the cross correlation between the stock market volatility and online financial news emotional intensity by MF-DCCA model. Empirical results show that there exist cross correlation between the stock market and online financial news emotional intensity and posse multifractal features. There exists an antisustainability between the stock market volatility and online financial news emotional intensity.