In order to improve the resolution further, the laser probe optical system was redesigned and optimized. The ultimate resolution of the laser probe based on far-field optics was studied. Using the reflex objective (N.A=0.4) to focus the incident 532 nm laser beam, under the condition of appropriate energy, the resolution of 2.26 μm and 1.87 μm on pure Al and Fe samples surface was obtained, respectively. Under this system, the effective Al and Fe atomic spectrum can be acquired with intensity three times of the background noise, respectively. A set of coaxial confocal imaging system with coaxial illumination was designed and realized, the field magnification is 24.7. The results showed that the coaxial illumination system can improve the sharpness and identification of the graphics with resolution not less than 228 lines per millimeter. A coaxial spectral collection system with indicator was invented, which can maintain the alignment error within 10 μm between the plasma and the coaxial collection system. In the coaxial monitoring area and combining with an X-Y axis scanning system, a spectra matrix with 63 points on the plasma surface can be acquired, which the images of plasma spatial resolution could be obtained.