The study establishes mixed-frequency vector autoregression (MF-VAR) model by combining the data of actual trade intensity, per capita energy consumption and per capita carbon emissions. The dynamic relationship between carbon tariffs and foreign trade under the transformation of low-carbon economy is analyzed through the descriptive analysis of sample data, unit root, cointegration, Granger causality tests, impulse response and ANOVA, and other econometric methods. The econometric results show that there is a long-run equilibrium relationship between trade intensity, per capita energy consumption and per capita carbon emissions. The three data variables have time series smoothness at 5% and 1% significance. There is 1 cointegration relationship between the variables at 5% significance level. The p-value of Granger causes is less than 0.05 and carbon tariff is the Granger cause of foreign trade in industrial goods. Impulse response analysis shows that the short-term impact of low-carbon economy on foreign trade is negative, but it gradually turns positive over time. The contribution rate of low-carbon economic development to foreign trade is around 16.1% in the short term and stabilized at around 26.2% in the long term. Constructing a synergistic policy of carbon mechanism and carbon tariff is of great value in accelerating the transformation and development of low-carbon economy and enhancing the total amount of foreign trade.