Trade has been an important force which shapes the industrial spatial pattern of Guangdong province. It is of great importance to conduct research on the relationship between export trade and firm agglomeration in Guangdong. From the perspective of multidimensional proximity between export destinations and local markets, this paper puts forward a new insight for the firm agglomeration in Guangdong, which has certain theoretical and practical significance. This paper argues that, the lower the proximity of a firm’s export destination to the local market is, the more difficult it is for the firm to directly gain comprehensive knowledge about the export destination at a distance. In this case, firms tend to agglomerate, in order to absorb the spillovers of relevant knowledge locally and achieve market expansion. Based on the data of China Customs Trade Statistics from 2002 to 2016, this paper describes the pattern of export markets and agglomeration of firms in Guangdong, and empirically measures the relationship between firms’ agglomeration level and the geographical, economic, political, institutional and cultural proximity between export destination and local market. In particular, the DO method is used to quantitatively measure the agglomeration level, which restores the original and micro form of firm agglomeration, making up for the shortcomings of the existing methods used to measure agglomeration level to a certain extent. Descriptive analysis shows that, on the one hand, the export markets of Guangdong’s firms are diversified, while the expansion of markets follows the principle of “proximity” to a certain extent. On the other hand, the distribution of firms presents an obvious “core-periphery” pattern. The empirical results show that when exporting to markets with low economic, political and institutional proximity to the local market, firms are more agglomerated. The geographical and cultural proximity has no significance effect on the agglomeration level of firms. At the same time, this effect is heterogenous in the sample of firms whose export markets are developed and developing regions.