Practical strategy for the thermal evaluation of film-cooled blade is of great importance to the gas turbine community. Due to the physical or methodology limitations, it is difficult to evaluate the blade’s thermal performance at simulated engine conditions. The present study proposed novel focal-sweep-based phosphor thermometry for blade cooling inspection. While Mg4FGeO6:Mn (MFG) served as the temperature sensor to quantify the blade temperatures as well as simulated the thermal barrier coating (TBC) effect, the focal sweep method was adopted to overcome the optical constraints in cascade testing. The obtained MFG results of microstructures, jet impingement, and anti-erosion test demonstrated that the MFG phosphor is robust enough to simulate the thermal insulation effect of TBC and can withstand high-speed flow erosion. Furthermore, the proposed strategy clearly captured the blade temperature distributions (mainstream at ) with high spatial resolution, which was then successfully remapped onto the three-dimensional twisted blade. Additional comparisons with the thermocouples demonstrated that the simulated TBC has a thermal insulation effect of about 68 K. This study addressed the common problems of phosphor thermometry in blade cooling evaluation, offering a practical strategy for future thermal diagnostics of the gas turbine.