Abstract: Abstract: Focused on the market entry order of exporters in new product-market portfolio and based on the matched big data of China's Customs Database and Chinese Industrial Enterprise Database during 2000-2006, this paper creatively raises and answers two questions respectively. Firstly, is the choice of market entry order of exporters based on the "self-selection" of these firms' productivity? The results prove that the more productive firms tend to be pioneers and the less productive ones tend to be followers. Moreover, the results based on the product classification further indicate the self-selection effect is more significant in exporting manufactured, but not obvious in exporting primary goods and agricultural goods. Secondly, does market entry order have an impact on the growth rate of firms' productivity after exporting? The results verify that in the short time, the growth rate of productivity is higher in followers than in pioneers, but with the advantage of pioneers becoming more obviously over time, their growth rate of productivity is apparently better than followers.