It has been over a decade since the new-new trade theory was born, the trade theorists expanded the more detailed and fruitful research on the hypothesis of firm heterogeneity. It was remarkable that the theoretical literature trade intermediaries were integrated into the analysis, which broke the limitations of direct export in existed research and which explained the influence of intermediary technology and incomplete contracts on the different export decisions and welfare distribution between direct export and intermediary export based on the firm heterogeneity and endogenous boundary respectively. This paper reviews the recent theoretical literature on heterogeneity and trade intermediary theory, illustrates the microscopic mechanism of the integration of trade intermediation into new-new trade theory and prospects its future development direction.