When a laser engraving machine carries out laser engraving, sometimes the laser "bursting points" are uneven. It is necessary to amplify and analyze the laser "explosion points" to better control the energy of the laser beam. A zoom microscope objective with long working distance was designed according to the observation requirements of "explosion points". The "explosion points" inside the glass have the viewing range of 9-32 mm. The zoom range of focal length is from 6 mm to 24 mm with optical zoom mechanism. The magnification is 4×-16×, and the zoom ratio is 4. A 1/2-inch CCD model VA-1MG2 was adopted as the detector with pixel size 5.5 ?滋m. The optical system optimization was carried out by using Zemax. The MTF values of all fields are larger than 0.4 at cut-off frequency 91 lp/mm for each configuration. The MTF values for central field and 0.707 field approach to the diffraction limit. The RMS radius of the spot diagram is smaller than the radius of Airy disk. The image quality of the designed system meets the requirements of all technical indicators.