With microscopic thermogravimetric analysis, it is difficult to prepare metastable intermediate phases with precise water contents during the dehydration process of hydrates, making it a challenge to acquire their related spectra. The gradual dehydration process of ZnSO₄·7H₂O proceeds through 7 → 6 → 4 → 1 → 0. Vibrational spectra of ZnSO₄ hydrates, especially ZnSO₄·6H₂O and ZnSO₄·4H₂O, have not been previously reported. By macroscopic thermogravimetric analysis of ZnSO₄·7H₂O, the dehydration process can be precisely controlled to produce a variety of ZnSO₄ hydrates with specific water contents. In this study, powder X-ray diffraction confirmed the purities of 7H₂O, 6H₂O, 4H₂O, 1H₂O and anhydrous ZnSO₄. IR and Raman spectra of ZnSO₄ hydrates were obtained and compared for the first time. Spectroscopic and crystallographic analysis revealed that structural similarity plays a key role in the 7 → 6 → 4 → 1 → 0 dehydration process. Macroscopic thermogravimetric analysis combined with powder X-ray diffraction is a valuable method for investigating the intermediate phases in the hydrate dehydration process.