Environmental benign and stable kesterite Cu2ZnSnS4 (CZTS) photovoltaics provides an intriguing alternative to conventional solar cells. However, further development is required for boosting the Voc-deficit in CZTS photovoltaic to enhance the cell function. Intending to obtain high-quality CZTS powder as the basis, here we report a comprehensive study of the vacuum annealing process (including annealing temperature, duration, and heating rates) for synthesized powder with the ball-milling method, which leads to a high-quality kesterite structure. According to analysis outcomes, there are not any significant differences in structures of differently milled specimens while the optical and morphological findings exhibit distinctive results. In short, the 10 h milled powder annealed at 500 °C for 5 h with a 9 °C min−1 heating rate possesses a high-quality structure alongside the desired 1.53 eV bandgap and optimum morphological characteristics.