Abstract: miRNAs played an important role in abiotic stress,and miR398a and pre-miR398a sequences were obtained from Small RNA database of Chrysanthemum×grandiflora. The sequence alignment showed that the cgr-miR398a was highly conserved with the identified miR398a sequences of other plants. Target genes prediction of cgr-miR398a showed that their annotation of targets include superoxide dismutaseCu-Zn（CSD2）,copper chaperone（CCS）,A20/AN1-like zinc finger family protein（SAP8）. The qPCR assay showed that the expression levels of miR398a was significantly decreased while target genes showed contrary trend during salt stress in Chrysanthemum×grandiflora. To explore the function of cgr-mir398a in response to salt stress,and an overexpression vector of cgr-mir398a was constructed and transformed into Arabidopsis thaliana.The result showed that overexpression of the cgr-MIR398a in Arabidopsis could decrease seed germination under salt stress and salt tolerance at the adult seedling stage,therefore cgr-miR398a played a negative regulatory role in Arabidopsis in response to salt stress. The results provided a valuable reference for further exploring the functional mechanism of miR398a during salt stress in Chrysanthemum×grandiflora.