Abstract: Provided is a method for regulating the symbiosis of gramineous plants and arbuscular mycorrhizal fungi or regulating the inhibitory effect of high phosphorus on mycorrhizal symbiosis, the method comprising: adjusting the expression or activity of the phosphorus starvation response factor PHR2 in gramineous plants. Also provided is the use of PHR2 or an encoding gene thereof in regulating the symbiosis of gramineous plants and arbuscular mycorrhizal fungi, regulating the inhibitory effect of high phosphorus on mycorrhizal symbiosis, and as a molecular marker for the identification of the symbiosis of gramineous plants and arbuscular mycorrhizal fungi. Also provided is a method for using PHR2 to screen for substances that regulate the symbiosis of gramineous plants and arbuscular mycorrhizal fungi or regulate the inhibitory effect of high phosphorus on mycorrhizal symbiosis. Also provided is a method for using PHR2 to identify mycorrhizal-associated genes regulated by PHR2 in mycorrhizal symbiosis.