Abstract： Objective:Through quantitative comparison of the gas supply performance of first-stage decompressors of different self-contained underwater breathing apparatus（SCUBA）at home and abroad，to provide a point of reference for the selection，design，and evaluation of SCUBA.Methods:Through the unmanned performance test，the gas supply performance data of first-stage decompressors（14 models）with different input pressures（3.5 MPa，12.0 MPa，20.0 MPa）were recorded，and the distributions of the differences in static outlet pressure，dynamic pressure drop，dynamic and static pressure difference，and maximum gas supply flow were statistically analyzed.Results:The differences in dynamic pressure drop（ P=0.007 at 3.5 MPa， P=0.006 at 12.0 MPa， P=0.034 at 20.0 MPa），dynamic and static pressure difference（ P=0.005 at 3.5 MPa， P=0.002 at 12.0 MPa， P<0.001 at 20.0 MPa）with three input pressures，and the maximum gas supply flow（ P=0.002）with 3.5 MPa input pressure were statistically significant. The differences in static outlet pressure with three input pressures，and the differences in the maximum gas supply flow with 12.0 MPa and 20.0 MPa were not statistically significant（ P>0.05）. Conclusions:The first-stage decompressors of foreign brands show better performance than those of domestic brands in terms of dynamic pressure drop，dynamic and static pressure difference，and maximum gas supply flow.