<p>The continuous cooling transformation significantly affects the final microstructure, which in turn determines the material’s ultimate properties. Controlling continuous cooling conditions is crucial for obtaining high-strength, high-performance spring steel 55SiCr. This study investigates the effect of deformation temperature and cooling rate on phase transformation through continuous cooling experiments, combined with hardness testing, scanning electron microscopy, and electron backscatter diffraction characterization methods. It constructs expansion curves, phase fractions, continuous cooling transformation curves, and phase transformation kinetics curves. Expansion curves, phase fractions, continuous cooling transformation curves, and phase transformation kinetics curves were constructed. The results show that 55SiCr steel has two transformation regions. At a deformation temperature of 800 °C, when the cooling rate is 5 °C/s or below, the transformation is from pearlite in the high-temperature region; when the cooling rate exceeds 5 °C/s, the transformation shifts to martensite in the low-temperature region. At a deformation temperature of 950 °C, martensitic transformation occurs even before the cooling rate reaches 5 °C/s. The Johnson–Mehl–Avrami (JMA) model shows that the pearlitic transformation follows the classic “S”-type diffusion transformation trend. As the cooling rate increases, the “S” curve shifts to lower temperatures, the transformation rate decreases, and the Avrami exponent (<i>n</i>) decreases, indicating that the growth mode of pearlite changes from three-dimensional to two-dimensional growth. High deformation temperatures promote dynamic recrystallization and provide more nucleation sites for martensite formation, while low deformation temperatures are more favorable for diffusion-controlled phase transformations, increasing the transformation temperature range and critical cooling rate for martensite.</p>