Abstract: In this study, Atmospheric Room Temperature Plasma (ARTP) technique was used to screen a original strain of amylase-producing Priestia koreensis FS-1. Results showed that a mutanted P. koreensis FS-103 with improved enzyme activity and stable genetics was obtained by the technique and its amylase activity was 90% higher than that of the original strain. To analyze the molecular mechanism that increase the enzyme activity of the screened strain, whole genome resequencing and comparative analysis was used to study the mutanted strain P. koreensis FS-103. Results show that the genetic variations in acetylation, antioxidant activity and synonymous mutation were found in P. koreensis FS-103. While the up-rugulation of differential gene expression involved in transcription, translation and post-translation modifying process were found in the functionalenrichment analysis of COG (clusters of orthologous groups) and the varianted genetics. As conclusions, it indicates that the up-regulations of the serial functuional expression gene of the mutanted strain P. koreensis FS-103 are the key reason for the improved enzyme activity.