This study aims to determine the effect of profitability, asset structure, growth, and liquidity on capital structure with company size as a moderating variable. The sample of this study were 71 manufacturing companies listed on the Indonesia Stock Exchange in the 2017-2019 period. So that the research data were 213 observations. The sample selection technique in this study using purposive sampling technique. The data analysis technique used in this research is descriptive statistics, classical assumption test, multiple regression analysis with interaction moderation method. The results of this study indicate that profitability, asset structure and growth have a negative and significant effect on capital structure. Meanwhile, liquidity has a positive effect on capital structure. And this study also shows that company size can moderate profitability, asset structure, growth and liquidity on capital structure.