To address the limitation of traditional micro-ring resonator thermometry, which relies on tracking a single resonance peak, thereby restricting the measurement range to within the free spectral range, we propose a wide-spectrum microcavity temperature measurement method based on the matching of transverse electric (TE) and transverse magnetic (TM) mode spacing. A temperature measurement system was constructed, comprising a widely tunable laser, a silicon nitride micro-ring resonator, a Fabry-Pérot interferometer, and a water vapor absorption reference unit. Employing a two-stage calibration strategy that combines relative wavelength scale calibration with absolute wavelength anchoring, the system extracts the center wavelengths of resonance peaks and establishes a standard library of mode spacing values, thereby enabling temperature retrieval. Experimental results demonstrate that within the temperature range of -10℃ to 40℃, the mode spacing exhibits a strong linear correlation with temperature, yielding a coefficient of determination of 0.998. The measured temperature sensitivity for the TE single mode is 18.356 pm / K, while that for the TM single mode is 17.283 pm / K. The temperature measurement error of the traditional single resonance peak tracking method is ± 0.05 K, while the error of the microcavity broadband temperature measurement method based on mode spacing matching is ± 0.035 K. This approach not only improves measurement accuracy but also expands the measurement range, enhances system robustness and response efficiency, and provides important references for the engineering applications of microcavity photonic temperature measurement.