Most plants can form a symbiosis in root with microorganisms for mutual benefit, Nonlegumes mainly form the symbiotic mycorrhiza with arbuscular fungi. The interaction is initiated by invasion of arbuscular mycorrhizal (AM) fungi into the plant root, and follows by production of several special signal molecules, such as the symbiosis receptor-like kinase (SYMRK) from plant. SYMRK has an extracellular domain comprising three leucine-rich repeats (LRRs), a transmembrane domain and an cytoplasmic protein kinase domain. Symrk is required for a symbiotic signal transduction pathway from the perception of microbial signal molecules to the rapid symbiosis-related gene activation. Study of symrk may set up a solid foundation for giving further insight on the function and mechanism of plant-fungi symbiosis.