Total pressure gain is one of the most significant performance metrics for rotating detonation engines. In this study, total pressure gains of kerosene-hot air(523K∼553 K) RDE for different combinations of A8/A3.2 and A3.1/A3.2 are measured by EAP(Equivalent Available Pressure).It is found that total pressure gain tends to increase with the decrease of A8/A3.1.The highest total pressure gain of -15% occurs at A8/A3.1 = 0.87.And the highest total pressure gain of each configuration approximately increases linearly with the decrease of A8/A3.1 with the maximum deviation of 3.3% for the same A8/A3.1 under different combustor widths. The total pressure gain climbs with the decrease of Pt2/P3.2. And there appears a clear demarcation point at Pt2/P3.2 of 1.89 for the effects of Pt2/P3.2 on total pressure gain because of different total pressure loss mechanisms. The equation of total pressure gain is rewritten to separate inlet losses from other losses. Positive total pressure gain is obtained when inlet losses are excluded for some cases. In order to take the effects of equivalence ratios, types of fuel, combustion efficiency and widths of combustion chamber on total pressure gains into account, Qv is introduced which is defined as the actual heat released by the combustion of fuel entering the combustion chamber for 1 hour in unit pressure and unit combustion chamber volume. There appears to be an approximately linear trend in pressure gain as a function of Qv for each A8/A3.1 A simple pressure gain model is developed to describe the variation of total pressure gain with A8/A3.1 and Qv. Higher Qv and lower A8/A3.1 are required to achieve positive total pressure gain which is not easy to be realized at the same time. As an important parameter for calculation of Qv, the average pressure of combustion chamber is approximately equal to the product of velocity of detonation waves and mass flux of nozzle outlet. A comparison is made among total pressure gain measured by EAP, (Mach-Corrected Static Pressure)and MFF(Mass Flow Function). They are basically linear with relative errors falling within +/-10%.