<p>The combustor is the primary energy-conversion component of an aero-engine; analyzing the unsteady characteristics of turbulent combustion helps to clarify the flame structure inside the combustor. At present, the investigation of unsteady characteristics in turbulent combustion flow fields is largely confined to Fourier-transform-based techniques, and most numerical models still belong to the flame-sheet family. To overcome these limitations, signal-analysis tools, such as Empirical Mode Decomposition (EMD), Continuous Wavelet Transform (CWT) and Cross-Spectrum Wavelet Transform (CSWT) have been adapted to the analysis of unsteady characteristics in turbulent flames. A high-fidelity compressible LES-TPDF approach, which affords excellent resolution of pressure fluctuations, is employed to simulate the flow field of an integrated flameholder combustor, and the aforementioned diagnostic techniques are applied to elucidate its unsteady characteristics. For three characteristic points, the dominant frequency of pressure fluctuations obtained from combustion experiments is 126 Hz. By the reacting simulation data, the dominant frequency is 104 Hz with FFT and 117 Hz with CWT. Due to the lack of heat release from chemical reactions, the dominant frequency decreases to 78 Hz with non-reacting simulation. Additionally, the dominant frequency fields and amplitude fields of pressure, temperature, and velocity fluctuations are analyzed. The results indicate that near the recirculation zone, temperature fluctuations are primarily controlled by flow dynamics, an influence that diminishes with axial distance until it disappears; after which temperature fluctuations are entirely governed by the intensity of chemical reactions. Furthermore, the analysis of the Rayleigh number (<i>Ra</i>) field reveals alternating regions of high and negative <i>Ra</i>.</p>