Abstract: Plant parasitic nematodes pose a serious threat to agricultural production and result in significant economic losses in crops worldwide. A key factor in crop production is plant resistance or susceptibility to nematodes; therefore, this has been an important subject for researchers in the areas of crop genetics and breeding. Understanding the mechanisms of plant resistance or susceptibility to nematodes is of great theoretical significance and practical value to guide the breeding of nematode-resistant crops. In this paper, the mechanisms underlying plant resistance or susceptibility to nematodes are reviewed, including specific plant resistance genes or proteins, plant hormone synthesis and signaling pathways, and reactive oxygen signals that are generated in response to nematode attack. In recent years, many researchers have suggested that plant resistance or susceptibility to invading nematodes and nematode-secreted effectors is mainly determined by the coordination of different signaling pathways. Many studies have shown that crosstalk among various nematode resistance-related elements represents an integrated signaling network regulated by transcription factors and small RNAs at the transcriptional, posttranscriptional, and translational levels. Ultimately, the outcome of this highly controlled signaling network determines the resistance or susceptibility of the host plant to nematodes. These above-mentioned results lay the foundation for further research on the signal transduction and regulation mechanisms involved in the plant-nematode interaction, and thus, provide a theoretical basis for the development of new strategies to prevent and control plant nematodes.