Rare-earth orthoferrites (RFeO₃) have received significant attention due to their intricate magnetic interactions and potential applications in ultrafast spintronic devices. Among them, DyFeO₃ exhibits rich magnetic phase transitions driven by the interplay between Fe³⁺ and Dy³⁺ sublattices. Previous studies mainly focused on temperature-induced spin reorientation near the Morin temperature (T_M~50 K), but there has been limited exploration of magnetic phase behavior under external fields above T_M. This work aims to systematically investigate the temperature- and magnetic-field-dependent magneto-dynamic properties of a-cut DyFeO₃ single crystals, with an emphasis on identifying novel phase transitions and elucidating the underlying mechanisms involving Fe³⁺-Dy³⁺ anisotropic exchange interactions. High-quality a-cut DyFeO₃ single crystals are grown using the optical floating zone method and characterized by X-ray diffraction (XRD) and Laue diffraction. Time-domain terahertz spectroscopy (THz-TDS) coupled with a superconducting magnet (0–7 T, 1.6–300 K) is employed to probe the ferromagnetic resonance (FM) and antiferromagnetic resonance (AFMR) modes. By analyzing the frequency trends in the spectra, the response of internal magnetic moments to external stimuli can be inferred. In the zero magnetic field experiment, it is found that the temperature induced spin reorientation (Γ₄→Γ₁) occurs at Morin temperature (~50 K) with temperature decreasing. A broadband electromagnetic absorption (0.45–0.9 THz) occurs below 4 K, which is attributed to electromagnons activated by broken inversion symmetry in the Dy³⁺ antiferromagnetic state. Above the Morin temperature, the absorption spectra of the sample are measured at constant temperatures (70, 77, 90, 100 K) and magnetic fields ranging from 0 to 7 T. The experimental results show that with the increase of magnetic field, a new magnetic phase transition occurs (Γ ₄ → Γ ₂₄ → Γ ₂ → Γ ₂₄ → Γ ₂ ), and the critical magnetic field of the phase transition varies with temperature. The phase transitions arise from the competition between external magnetic fields and internal effective fields generated by anisotropic Fe³⁺-Dy³⁺ exchange. These findings contribute to the further understanding of the magnetoelectric effects in RFeO₃ systems and provide a roadmap for using field-tunable phase transitions to design spin-based devices .