A novel optical system is proposed for generating approximate non-diffracting grating structure light,and it is composed of several triangular-section prisms.The technical problem that the striped regional of approximate non-diffracting grating structure light generating by existing technology is so small that it cannot be applied to wide range measurement is solved.Physical processes of generating approximate non-diffracting grating structure light is analyzed by interference theory,and relevant parameters are also calculated.The intensity distribution in different positions after system is simulated by Zemax software.The conclusion of simulation is consistent with that of interference theory.And impacts on output beam by several systematic errors are also analyzed.The result shows that when a plane wave illuminates on the novel optical system,approximate nondiffracting grating structure light with wide measurement area,adjustment flexibility and strong anti-interference ability is formed.