In order to improve the preparation method, nano-sized MIL-101(Cr) was synthesized with the addition of tetramethylammonium hydroxide（TMAOH）through hydrothermal method and improved solvent replacement method. The obtained nano-MIL-101 (Cr) was of uniform particle size and high porosity. The synthesized MIL-101(Cr) was characterized by PXRD、SEM、TG、CHN and N2 adsorption measurements. The results revealed that the improved solvent replacement method greatly shortened the post-treatment time. When the TMAOH was added with an amount of 1 mmol, the nano-MIL-101 (Cr) with a particle diameter about 93 nm and a BET surface area about 3 500 m2 /g could be prepared. PXRD, SEM, TG, CHN elemental analysis and N2 adsorption desorption experiments showed that the product was not only of great purity, but also of very high porosity. The new method could be used to prepare nano-MIL-101 (Cr) in a simple and efficient way to expand its application prospect.