Sanitary and phytosanitary （SPS） measures are the main non-tariff measures for the trade of agricultural products under the framework of WTO. The importing countries set SPS measures， based on the consideration of preventing risks， protecting consumers， and protecting plants and ecological environment from being damaged by the exotic pathogens， biology and insect pest carried by agricultural products. However， SPS measures can easily be overused as trade barriers restricting foreign products. Therefore， the impact of SPS measures on the export of agricultural products has been the focus of scholars' research， but there has been scant research on the impact of the same SPS measures on the country of different levels of development. In fact， as a product quality threshold， the compliance cost of SPS first affects an enterprise's market entry behavior， followed by the impact of trade flow， i.e. SPS measures affect the binary boundary， the breadth and the depth of agricultural products. Confronting the SPS measures of importing countries， especially developed countries， the export enterprises of developed countries have more compliance advantages than those of developing countries in terms of capital， talent， technology and supply chain system. Trade may divert from developing countries to developed countries. The trade diversion effect in theory has not been verified in empirical analysis yet. Based on the firm heterogeneity assumptions of new-new trade theory， this paper analyzes the difference impact of SPS measures on heterogeneous firms， and then empirically test the trade diversion effect of SPS measures by adopting China's import trade data of agricultural products （HS01-24） between 1995 and 2013， and the data from such developed countries as EU， Australia， Japan， the United States， and Canada， and by employing the Heckman's two-step method. It has found out that in the first and second years when SPS measures are implemented， trade diversion effect is ambiguous because of the principles of differential treatment for developing countries in SPS agreement， and the resource endowment of agricultural production. However， in the third and fourth years of implementation， the import source of agricultural products from developing countries switches to developed countries. Based on the weaknesses of developing countries in the SPS measures， international organizations such as the standard and trade development facilities have been helping the traditional industries in developing countries since 2004 to adapt to the SPS measures of developed countries. The trade diversion effect of SPS measures will be beneficial to China， the world's largest importer of agricultural products， who can increase import quality and safety level of agricultural products by implementing SPS measures. But this will challenge China as an exporter of agricultural products as it requires China's export enterprises to take the opportunity of complying with the foreign SPS measures to improve product quality by upgrading their technological level and increasing the fixed investment in the industrial chain of agricultural products．