According to the demand of the condition monitoring system of scramjet inlets, 2-D flow field of the scramjet inlets was numerically simulated; the numerical simulation results of the scramjet inlets at different Mach number and different pressure were presented. The surface static pressure distributions of the inlets from start to un-start was analyzed and the start judgment criterion was given. After inlet monitoring parameters are determined, extension theory was applied to the sensor selection, thus establishing a comprehensive evaluation method of scramjet sensor selection. Then An example of pressure sensor using this optimal selection method verified the effectiveness of this method. The research provides reference for the establishment of the scramjet parameters measurement scheme and the design of condition monitoring system.