Abstract: To clarify the degradation mechanism of monomer-polymerized gels by oxidative gel breakage at the end of temporary plugging operations, a degradation kinetics study on the oxidative breakage of gels was carried out. The Horowitz-Metzger, Coats-Redfern, and Flynn-Wall-Ozawa models were used, and the degradation kinetics parameters of ultra-high-strength gel (USGel) were calculated. The degradation kinetics model suitable for USGel was obtained by comparative analysis. By combining with the scanning electron microscope, Fourier infrared spectroscopy analysis, and other experiments, the degradation and breakage mechanism of USGel by gel breakers were revealed, and the modified degradation prediction models for low, medium, and high temperatures were obtained. The results show that the models are suitable for predicting the degradation time of USGel at medium and high temperatures. According to the gel degradation mechanism, the gel breaker gradually consumes the chemical bonds such as the amino group (−NH2) of the USGel amide group and the hydroxyl group (−OH) of the carboxylic acid group, and the polymer molecular chain is gradually broken. Finally, the USGel is broken into liquid. The results provide a theoretical basis for the improvement of the temporary plugging and gel breakage technology of oil and gas wells.