In this study, the phenotype and genotype of powdery mildew resistance in 36 pea cultivars or lines introduced from Canada were identified, and the allele at powdery mildew resistance gene er1 locus in cultivars Cooper and Tara were investigated. All tested cultivars or lines were inoculated by two powdery mildew isolates from different geographical origins in seedling stage, respectively. Thirty-two cultivars or lines were immune to the two isolates, and line MP1818-2 was immune to isolate EPYN and susceptible to isolate EPBJ, whereas 3 cultivars were susceptible to the two isolates. Five marker genotypes were identified in the 36 cultivars or lines by 4 SCAR markers linked to er1. Sequence analysis revealed that both PsMLO1 candidate gene in Cooper and Tara contained a point mutation which G replaced C of PsMLO1 gene at 680 bp site.