The combustion oscillation characteristics in the lean premixed prevaporized (LPP) combustor at different equivalence ratios and inlet velocities of the combustor were experimentally investigated. Acoustic modal analysis was carried out to identify the acoustic eigenmodes in the LPP combustor. The flame structures under different operating conditions were investigated. The evolution laws of flame structures, coordinates and velocities of the flame centers, and heat release rates throughout a combustion oscillation cycle were investigated by phase-locked OH planar laser-induced fluorescence (PLIF). The result shows that there is a periodical process of flame roll-up for the flame close to the LPP combustor axis and a periodical process of separation and consolidation for the flame far from the LPP combustor axis. The spatial distribution of the normalized Rayleigh index in the LPP combustor was calculated to determine the driving zones of the combustion oscillation. The mechanism of combustion oscillation in this LPP combustor was identified by the analysis of the flame structures, heat release rates throughout a combustion oscillation cycle, and the spatial distribution of the normalized Rayleigh index.