Active thermal protection component is an important structure in the field of aerospace. Fiber laser welding is the preferred manufacturing technique for this kind of structure. Stringent service environment puts forward higher comprehensive requirements for weld forming, surface protection, and porosity defects. Based on the side protective fiber non-penetrate deep penetration laser welding process test, the effects of phosgene spacing, gas transmission angle, protective gas output length and gas flow rate on weld formation, and weld protection and porosity were systematically analyzed by means of ultra-depth of field microscope, digital RT detection, and gray scale processing. The results show that the shielding gas flow rate and distance between the laser and the protective gas have a great influence on the weld morphology and porosity. Under the condition of positive distance between the laser and the protective gas, the weld porosity is low, and the porosity is positively correlated with the shielding gas flow rate. Based on the optimized gas protection parameters, the nozzle structure was optimized, and the 3D component of active thermal protection groove was manufactured by laser welding, which passed the bench test.