Our simulations revealed that a highly localized optic-thermal transformation can lead to high temperatures in the fiber-based metallic Fabry-Perot cavity (FMFP) due to optical resonance. Both the transfer matrix method and finite difference time domain (FDTD) method are used for optical analysis of FMFP. Empirical formulas of maximum temperature were derived based on the superposition principle. Despite the fact that the derivation of the resonance condition for FMFP is usually discarded due to its complexity, we propose a simple resonance condition for a metallic Fabry-Perot cavity. In addition, suddenly tuning on the incident light will cause fast-decaying air pressure and velocity, which are also solved from nanosecond scale to equilibrium. This paper is useful for estimating the heat tolerance threshold of nanostructures on fiber end surfaces. Photothermal conversion in FMFP provides an excellent miniature heat source for applications that require high-efficiency photothermal conversion, and FMFP is particularly suitable for optofluidics.