Various nonmetallic materials such as PMMA and wood products have been conducted by CO_2 lasers.The mechanism of evaporative CO_2 laser cutting nonmetallic plates was discussed.A theoretical model based on energy balance was presented that predicted the cutting depth with respect to material properties and cutting speed.Experimental results are found to be in good agreement with theoretical calculation.The model is applicable to laser cutting thinner plates with the thickness less than 6 mm.The ability of low power level laser cutting nonmetallic materials was analyzed by considering the theoretical model.In order to improve the cutting efficiency,a new concept of preheated gas jet laser cutting was introduced.