In this study, five kinds of straw extracts (rice, wheat, corn, soybean and sweet potato) were used to investigate their effects on AM fungi inoculation and the components of these straw extracts were identified as well. The results showed that root colonization was significantly improved by adding rice, wheat, corn and sweet potato straw extracts. Dry weight and shoot P concentration were both significantly increased by rice straw extract. Main chemical?components of each straw extracts identified by GC-MS analysis were phenolic acids, which may play an important role in regulating AM fungi.