Mating type, metalaxyl sensitivity and mt DNA haplotypes of 151 Phytophthora infestans isolates col-lected from Heilongjiang Province from 2012 to 2014 were determined in the study. The results of mating typeshowed that among the 151 P. infestans isolates, 103（68.2%） isolates were A1 mating type, which account for 68.2%; 33 isolates were self-fertility type, which account for 21.9%; 15 isolates were A2 mating type, which ac-count for 9.9%. The results suggested that the group structure of potato late blight fungus in Heilongjiang Provincehas changed obviously. The results of metalaxyl sensitivity showed that among the 151 P. infestans isolates, 3.3%isolates were sensitivity to metalaxyl, 6.6% isolates were moderate resistant to metalaxyl, and 90.1% isolates were re-sistant to metalaxyl. The results suggested that P. infestans isolates in Heilongjiang Province have been of metalaxylresistance. The results of mt DNA haplotype showed that three mt DNA haplotypes were found in the main potatoplanting areas in Heilongjiang Province. The three mt DNA haplotypes were Ia, Ib and IIa, respectively. Of which,the IIa type with the occurrence frequency of 86.1% was the most. The result suggested that IIa mt DNA haplotypewas the dominant population in the main potato planting areas in Heilongjiang Province.