A laser processing head (100) comprises a first-level nozzle (110) and a second-level nozzle (120) that communicate with each other, wherein the second-level nozzle (120) is arranged downstream of the first-level nozzle (110); an inner diameter of the second-level nozzle (120) gradually decreases in a laser transmission direction, and minimum inner diameter of the first-level nozzle (110) is larger than the inner diameter of a tail end of the second-level nozzle (120). The laser processing head (100) solves the contradiction between high energy density laser and the system reliability through gradual coupling. Also provided are an application of the laser processing head, a laser processing system and a laser processing method.
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