Characteristics of combustion oscillations were studied experimentally in a direct-connected supersonic combustion test facility with a cavity flameholder and transverse fuel injection from the wall. Static pressures were obtained by using high-frequency dynamic pressure transducers. The effects of inlet Mach number and fuel injection were examined. The frequency spectrum of wall pressures shows that combustion oscillations are different between the ramjet mode and the scramjet mode. In the ramjet mode, the high frequency combustion oscillations are on the same order of frequency as cavity oscillations. The low frequencies increase as inlet Mach number increase and fall in a range of 200-450Hz. In the scramjet mode, the high frequency combustion oscillations exist in trailing edge of the cavity, the frequencies are about 4 kHz and the occurrence is related with transverse injection momentum ratio. © 2015, AIAA American Institute of Aeronautics and Astronautics. All rights reserved.