Simple sequence repeats (SSR) and random amplification of polymorphic DNA (RAPD) molecular markers were used to assess the genetic diversity of 80 isolates of Phytophthora infestans in potato (Solanum tuberosum) from Fujian, Heilongjiang, Hebei and Inner Mongolia Provinces in China. Polymorphism was identified by 13 SSR primers and 14 RAPD primers in the isolates of P. infestans in potato. A total of 76 bands were amplified by SSRs, with the percentage of polymorphic bands (PPB) being 78.9% and the similarity coefficient ranging between 0.00 and 0.42. A total of 189 bands were amplified by RAPDs, with the percentage of polymorphic bands being 95.2% and the similarity coefficient ranging between 0.04 and 0.66. Analysis of genetic diversity showed that there exists higher genetic variation in the Fujian population in comparison to the populations of Heilongjiang, Hebei and Inner Mongolia. Nei's genetic identity analysis indicates that the genetic similarity between populations of Heilongjiang and Inner Mongolia is the highest and that between Fujian and Hebei is the lowest. A cluster analysis revealed that isolates from Fujian, in the south of China, are distantly related to those from Heilongjiang, Hebei and Inner Mongolia in the north, and the Fujian population is distributed among more groups than the other three, exhibiting a higher genetic diversity.