TGARCH model and VAR theory are used to study the volatility of the CSI 5G communication subject index. Empirical analysis found that 5G communication index has "leverage" effect, good information has a positive impact on stocks; By calculating VaR risk values with different distributions and different confidence levels, combined with Kupiec accuracy test, it is shown that at 95% confidence level, the fitting effect of TGARCH model based on t-distribution is the best.