The present disclosure discloses an AtPPR1 gene (negative regulatory factor) for Phytophthora resistance and homologous genes thereof, involving an AtPPR1 gene and a protein encoded by the AtPPR1 gene. The AtPPR1 gene has a nucleotide sequence of SEQ ID NO:6, and the protein encoded by the AtPPR1 gene has an amino acid sequence of SEQ ID NO:7. A function of the AtPPR1 gene of the present disclosure to improve Phytophthora resistance of plants can be used for the selective breeding of Phytophthora-resistant varieties. As a new type of negative immunoregulatory factor in plants, AtPPR1 negatively regulates the resistance of plants to Phytophthora by interfering with downstream signal transduction of endogenous jasmonic acid (JA) and salicylic acid (SA) and ROS signals in plants.