Abstract: This paper reports the preparation of chromium (Cr) - doped Bismuth Selenide (Cr-Bi₂Se₃) thin films by Molecular Beam Epitaxy (MBE). Cr-Bi₂Se₃ was tested by Reflective High Energy Electron Diffraction (RHEED), X-ray diffraction (XRD) and electromagnetic transport system. The experimental results show that most Cr atoms enter Bi₂Se₃ and replace Bi site to form Cr_Bi at low growth temperatures; At higher temperatures, a significant part of Cr atoms enter the van der Waals gap forming interlayer Cr_I, which leads to different magnetic properties of Cr- Bi₂Se₃. Therefore, we can adjust the Cr doping position by controlling the growth temperature to obtain a better effect.