Abstract: In order to study the role of JAR1 (At2g46370) gene in the mechanism of JA signaling, a mutant jar1 (SALK_030821) inserted by T-DNA was obtained from the Arabidopsis Biological Resource Center. The homozygous jar1 mutants were screened out after the position of T-DNA insertion were identified. The expression level of the JAR1 gene in jar1 mutants was analyzed by quantitative real-time qRT-PCR, JA sensitivity was detected, and the growth of the seedling in the medium containing MeJA was observed. The results show that the expression of JAR1 gene was dramatic reduction, it is about 41.2% of wild type plant. Comparing to the wild type, the sensibility of homozygous mutant jar1 seedling roots to MeJA was also decreased.