Early podding period of peanut plants were treated with 1 mmol/L and 0.1mmol/L of methyl jasmonate(MJ) and the results showed MJ treatment increased PI activity during seeds development of peanut(Arachis hypogaea L.) under disadvantageous condition(drought or inoculated with Aspergillus flavus).The treatment with high concentration of MJ was better than that with low concentration.PAL activity had similar result,but long-term effect of Mj affecting PAL activity was not obvious.