The maize leaves were pretreated respectively by low concentraion Helminthospolium maydisT-toxin(HMT-T),protein and cell-wall, which were extracted from cultivating filtrate at the stage of three-leaf, and then these leaves were treated by high concentration HMT-T and cultivated 5 d. The dimension of spots in infected leaves was calculated and phenylalanine ammonia lyase(PAL) activity determined. The result showed that only the HMT-T could act as elicitor in the cultivating filtrate. The suitable concentration of HMT-T was different for various varieties. As to TC103 the suitable concentration of toxin was 0.025 μg/mL and the PAL activity of maize leaves reached its maximum degree in this case. The right concentration of TB37 and TMo17 were 0.025 μg/mL and 0.050 μg/mL respectively.