TEPIX is a weighted average of market capitals, and known as market representative. On the other hand, the equal-weighted index was proposed as representative of all issuers with same weights, which can have a trend in favor of or against the TEPIX. The present study examines the impact of large-cap stocks on the capital market. This study measures the effect of the 30 large-cap stocks, as a representative of the stock prices of large capital market companies, on TEPIX and equal-weighted indices, by controlling the variables of trading value, exchange rate, and interest rate. Daily data in the period from 01/08/1399 to 01/03/1404 and two approaches have been considered: the ordinary least squares and Threshold Regression using the first difference of the variable. Based on the findings, by using first approach, the index of 30 large-cap stocks has a positive and significant effect on TEPIX and explains its behavior well, expectedly. The effect of large-cap stocks on the equal-weighted index is also positive, but its coefficient shows much weaker effect, which is about 25 percent of its effect on the TEPIX. By using threshold approach and after selecting the exchange rate growth variable as the transition variable and determining the threshold for the two exchange rate growth regimes and its reduction, the coefficient of the index of 30 large-cap stocks on TEPIX in the low regime is about 3.5 times its coefficient on the equal-weighted index, but in the high regime, the coefficient of the index of 30 large-cap stocks on TEPIX is half of that coefficient on the equal-weighted index.