Objective: To compare Melai azedarach L. and Melia toosendan Sieb.et Zucc. trying to see whether they can be seen as one herb. Methods: The properties, microscopic characteristics and TLC of the two medicinal materials were compared, and the content of toosendanin was determined by RP-HPLC. Results: There were some differences between the two medicines in their properties and microscopic characteristics. In TLC, using chloroform-methanol (16:2) as developer, Melai azedarach L. had one more component than Melia toosendan Sieb.et Zucc. The results of determination of toosendanin by RP-HPLC showed that it was higher in Melia toosendan Sieb.et Zucc. than that in Melai azedarach L.. Conclusion: Melai azedarach L. and Melia toosendan Sieb.et Zucc. are different in chem. composition and content, so they should be differentiated in medicinal use, can not be mixed or misused.