Late blight, caused by P.infestans, is the most distructive disease of potato (Solanumtuberosum).This study was aimed to understand the population genetic structure of Phytophthora infestans in Fujian, China, and inferred the evolutionary mechanisms governing the structure.534 isolates were sampled from eight locations in Fujian province from 2010 to 2012 and assayed the isolates with eight simple-sequence repeat (SSR) markers.30 alleles and 49 genotypes were detected among the 534 isolates.Clustering analyses reveal that P.infestans populations in Fujian province are made of three differentiated genetic clusters.Cluster A were self-fertility, while cluster B include mating types A1 and self-fertility, cluster C include only mating types A1.Further analysis indicated that Cluster C were likely to have experienced a recent population bottleneck.We propose that genetic variation of P.infestans population in Fujian is due to the infected seeds imported from other parts of China.The implications of these results are discussed.