[Objective] In order to obtain an industrial strain with higher xylanase production, the original strain of Saccharomonospora viridis was mutated by atmospheric and room temperature plasmas. [Methods] The methods used to screen the mutant strain with higher xylanase production included transparent loop diameter measurement of selective medium with 2% beech-wood xylan and shaking flask fermentation. [Results] It has been demonstrated that both mutants AT22-2 and AT24 maintain good genetic stability. The enzyme activity in the fermentation liquor of AT22-2 and AT24 at 7 d reached 552.70 U/mL and 512.74 U/mL, which were 17 and 16 times higher than that of the original strain, respectively. Furthermore, the op-timum pH and temperature values for xylanase activity of AT22-2 were pH 9.5 and 90 °C, re-spectively, being stable within a temperature range of 50 °C?90 °C, and showing high thermo-stability at 100 °C for the duration of 30 min. In addition, for another mutant AT24, the opti-mum pH and temperature values for xylanase activity were pH 10.0 and 60 °C, with a stability within a temperature range of 60 °C?80 °C. [Conclusion] The xylanase with thermostability and alkali-tolerance of mutant AT22-2 is a potential candidate for future use in biotechnologi-cal applications particularly in the pulp and paper industry.