Based on the results of calculation and measurement of the two kinds of marine gas turbine exhaust systems with the infrared signature suppression devices, according to the similarity theory, the effects of scale factor on the temperature profile (of air flow and tube wall), and infrared radiant intensity(of exhaust plumes and exhaust uptake inner wall) of the exhaust system were analyzed and discussed. Based on the corresponding parameters of real ship exhaust systems as well as the magnitude of scale factor impacts, the recommended values for selecting the scale factor were estimated and presented.