The 20mm carbon steel bright surface is a standard plate that demonstrates a cutting ability of 10000 watts. For verification, it employs a supersonic single-layer nozzle with an aperture of 1.2. The focus to defocus ratio is approximately +12.5, ensuring a superior cutting effect. However, using a hot nozzle for laser cutting heads during this process presents challenges for long-term stable cutting. Through optical software simulation of the laser head and actual beam analysis testing, results indicate that achieving a good cutting effect relies not only on the length of the focusing optical path but also on the total length of the optical path itself. The variation in cooling and light absorption devices within different cutting heads may be the primary reason that affects the outgoing beam under the same optical path.