The invention relates to the fields of microorganisms and phytopathology, and particularly discloses a method for counting plant pathogenic oomycetes zoospores. According to the invention, the cameraphase parameter is set, so that the two morphological characteristics of the zoospores, namely blue spores and orange spores, can be clearly observed, thereby realizing the counting of the zoospores.According to the method, the zoospores and the resting spores can be counted simultaneously, so that the related experiments of the oomycetes zoospores are facilitated, and the accuracy and the precision of experimental results are improved. The method disclosed by the invention is simple and reliable, and all microscopes with imaging equipment can be suitable for counting oomycetes zoospores, sothat an evaluation index is provided for evaluating the severity of plant diseases and the pesticide effect of the bactericide.