Abstract: In many fields,such as precise measurements,optical communication and laser processing,the non diffraction beam has useful advantage.Usually,a axial prism was utilized to obtain non-diffraction beam with a fixed θ parameter.In our investigation,we designed a novel optical system to generate a non-diffraction beam with changeable θ parameter.The system includes a negative axial prism and a lens system.In this paper,we proposed the design method of the system,the design parameters and the potential applications.