A test on venturi-type premixer of ASE120 engine combustor has been performed to evaluate its mixing performance. Cold air was supplied into the premixer through the fuel nozzle and mixed with the hot air from the compressor exit. The measured temperature of the mixed air was used to evaluate the mixedness. DOE(Design of Experiment) technique was utilized to make a test matrix of variables and to determine the optimum combination of variables, which was verified through a confirmation test.