MgSiO₃ perovskite is the most abundant material in the Earth's lower mantle. It is very difficult to obtain single crystal of MgSiO₃ perovskite due to its high pressure stability over 22 GPa. Thus synthesis of MgSiO₃ perovskite, especially the large grain size single crystal, is extremely important to investigate the properties of lower mantle. In this study, the details of synthesizing the single crystal of MgSiO₃ perovskite with large grain size were presented. Our synthesis experiments were conducted at a condition of 25 GPa and 1 500 ℃ using a 5 000 t Kawai-type multi-anvil apparatus. The results using different lengths of Pt capsule showed the large grain size perovskite crystal can also be obtained even at the large temperature gradient area in longer Pt capsule, which is different from previous experimental results. It is suggested that a large temperature gradient in the sample capsule can increase the nucleation density, however, it can also boost the crystal growth of perovskite and thus crystal can grow at a fast speed. Furthermore, the perovskite growth mechanism was investigated through analysis of twin crystal, which is important to understand the characteristics of the crystal growth of MgSiO₃ perovskite at high pressures.