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Phytophthora root rot is a destructive soybean disease worldwide, which is caused by the oomycete pathogen <i>Phytophthora sojae</i> (<i>P. sojae</i>). Wall-associated protein kinase (<i>WAK</i>) genes, a family of the receptor-like protein kinase (<i>RLK</i>) genes, play important roles in the plant signaling pathways that regulate stress responses and pathogen resistance. In our study, we found a putative Glycine max wall-associated protein kinase, GmWAK1, which we identified by soybean GmLHP1 RNA-sequencing. The expression of <i>GmWAK1</i> was significantly increased by <i>P. sojae</i> and salicylic acid (SA). Overexpression of GmWAK1 in soybean significantly improved resistance to <i>P. sojae</i>, and the levels of phenylalanine ammonia-lyase (PAL), SA, and SA-biosynthesis-related genes were markedly higher than in the wild-type (WT) soybean. The activities of enzymatic superoxide dismutase (SOD) and peroxidase (POD) antioxidants in <i>GmWAK1</i>-overexpressing (OE) plants were significantly higher than those in in WT plants treated with <i>P. sojae;</i> reactive oxygen species (ROS) and hydrogen peroxide (H₂O₂) accumulation was considerably lower in GmWAK1-OE after <i>P. sojae</i> infection. GmWAK1 interacted with annexin-like protein RJ, GmANNRJ4, which improved resistance to <i>P. sojae</i> and increased intracellular free-calcium accumulation. In <i>GmANNRJ4-OE</i> transgenic soybean, the calmodulin-dependent kinase gene <i>GmMPK6</i> and several pathogenesis-related (<i>PR</i>) genes were constitutively activated. Collectively, these results indicated that <i>GmWAK1</i> interacts with GmANNRJ4, and <i>GmWAK1</i> plays a positive role in soybean resistance to <i>P. sojae</i> via a process that might be dependent on SA and involved in alleviating damage caused by oxidative stress.