The effects of exogenous MeJA at five concentrations of 0.05,0.10,0.15,0.20 and 0.25 mmol·L^-1 on seed germination,seedling growth,the oxidative damage and the protective enzyme activities of the leaves of Perilla frutescens were measured under high air humidity (95%) for 12 hours at 50℃.The results indicated that the damages to the P.frutescens caused by the high temperature and air humidity were most significantly relieved by the 0.15 mmol·L^-1 MeJA.The seed germination rate,germination potentiality,germination index and vigor index increased to the maximum with 40.84%,31.83%,8.83 and 1.35,respectively.MDA content decreased to the minimum with 0.15 μmol·g^-1.The protective enzymes of SOD,CAT,LOX,POD and APX increased to the maximum with 0.27 U·mg^-1,4.7,5.7,4.9 and 8.9 U·g^-1·min^-1,respectively.Based on the data reported,we conclude that MeJA can relieve oxidative damage under high temperature and high air humidity stress,enhance the activity of protective enzymes and stimulate P.frutescens seed germination and seedling growth.