Abstract: The slow-axis of a high power diode laser stack is collimated and focused by a telescope system that consisted of two pieces of cylindrical lens.The stack is consisted of five diode laser array each power is 60W,and the central wavelength is 808nm.We test the waist sizes of the beam in the system consisted of different lenses,and study the affection of the cylindrical focal length on it.Beam paths of the telescope system are simulated by Zemax software,and the system aberration is analyzed.When the slow-axis collimating focal length is 200mm,the focusing length is 100mm,we can get the laser power density at 3.05kW/cm².Under these experimental conditions,the irradiation test of 316L stainless steel is conducted,vaporized groove is found on the plate and depth-to-width ratio is about 0.5.