The mix-based activated carbon derived from corn stalk and walnut shell was prepared by chemical activation method using phosphoric acid as the activator. The optimized conditions for preparation were obtained by the orthogonal experiment, the characterizations of the activated carbon were performed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy(FTIR), Boehm’s titration method and nitrogen adsorption. For the prepared mix-based activated carbon, the highest iodine number, methylene blue number and BET surface area are 720.5 mg/g, 195.0 mg/g and 1187 m 2 /g, respectively, and the pores are mainly mesopores. The mix-based activated carbon shows the higher adsorption capacity for malachite green than the raw materials, the activated carbons prepared only from corn stalk or walnut shell and the commercial activated carbon. The kinetics and thermodynamics of the adsorption can be satisfactorily described by the Pseudo-second-order kinetic model and the Langmuir isotherm model, separately.