A cardon-based solid acid catalyst was prepared and its characteristics were studied through FT-IR spectra, elemental analysis (EA), X-ray diffraction (XRD) analysis and thermogravimetrican analysis(TGA) . The catalyst was used in transesterification of Azadirachta indica oil with methanol，the relative factors influncing the transesterification were studied and the contents of TG，DG，MG and FAME were analyzed by HPLC analysis. The result showed that it was effective to use the cardon-based solid acid catalyst in catalyzing the transesterification of Azadirachta indica oil with methanol, and the best reaction conditions (the ratio of oil to methanol 1:12 ) were the ratio of catalyst to Azadirachta indica mass part 10 %, the reaction temperature 120 ℃, the reaction time 8 hours, the FFAs content less than 10 % in Azadirachta indica oil, the water content less than 5 % in Azadirachta indica oil and the ratio of transesterification was to 95 % .The catalyst was reused for 10 times while the ratio of transesterification would not decrease.