The present invention relates to a BCDA-based semi-alicyclic homo- or co-polyimide membrane material for gas separation and a preparation method thereof. The polyimide material prepared according to the present invention has high solubility in casting solvents, particularly in polar organic solvents, by interrupting asymmetry in the polyimide chain structure and formation of polyimide complexes compared with aromatic polyimides, and has higher heat resistance than the conventional aromatic polyimides and aliphatic polyimides, so that it is useful for the process of a high-selective permeable composite membrane or a asymmetric hollow fiber membrane used for commercial purposes, suggesting that it can be effectively used as a membrane for gas separation in various fields. In addition, the polyimide material membrane for gas separation of the present invention is useful because it has superior gas separation properties to the conventional commercialized aromatic polyimides or semi-alicyclic polyimides.