Spent grain is regarded as a natural adsorption material because of it is rough surface structure and functional groups. In order to realize the recyclization of the spent grain, etherified modified spent grain (MSG) for adsorbing methylene blue (MB) was prepared from raw spent grain (RSG) with NaOH as alkaline catalyst and chloroacetic acid as the etherifying agent. The effect of the modification parameters on the adsorption effect was investigated. The results showed that the adsorption of MSG reached maximum value with 201.20 mg/g, when the ratio of NaOH to ClCH2COOH was 2.5:2.0, etherification temperature was 75 ℃ and etherification time was 2.5 h. The morphology, specific surface area, pore size distribution and surface properties of RSG and MSG were analyzed by means of SEM, N2 desorption, FTIR, XPS and pHpzc. The absorption mechanism of MSG to MB dye can be well described by Langmuir equation and pseudo-second-order kinetic equation, indicating that chemical adsorption is the main adsorption method.