Abstarct: In this research, the stem of Acroptilon repens plant, as a low-cost and abundant agricultural pest, was modified using sodium hydroxide solution and characterized by FT-IR (Fourier Transform Infrared Spectroscopy). Then, the efficiency of this adsorbent for the simultaneous removal of cationic dyes methylene blue and crystal violet from aqueous solutions was evaluated. The effect of different laboratory parameters such as initial Ph of sample solution, amount of absorbent, contact time, initial concentration of dyes and ionic strength on the removal efficiency of this dyes in one-component and two-component systems was evaluated. According to these studies, pH equal to 7, the amount of adsorbent 0.035 g, contact time of 10 minutes and initial dye concentration of 20 ppm were selected as optimal values. Also, the isotherm studies performed on the adsorbent showed that the Freundlich adsorption isotherm is able to describe the equilibrium data well, and the Freundlich intensity factor for the two colors methylene blue and crystal violet in the two-component system is equal to 1.27 and 1.23 respectively. Kinetic studies of the absorption process also showed that the absorption process of two dyes, methylene blue and crystal violet, in each one-component and two-component systems follow pseudo-second-order kinetics. After that, by studying the thermodynamic parameters, according to the negative value of ∆G°, the spontaneity of the absorption process was confirmed. The positive value of ∆H° also showed the endothermic nature of the process and the positive ∆S° showed the increase of irregularity in the interface between the absorbent and the solution during this process. At the end, this adsorbent was recovered using a 0.1 M solution of ethanolic soda and dishwashing liquid, which showed 90% and 91% removal efficiency of dishwashing liquid for crystal violet color and methylene blue color, respectively. The removal efficiency of ethanolic soda solution was 88% for methylene blue dye and 89% for crystal violet. According to the results, it was reused up to 4 more times until the recovery efficiency of one of the colors reached below 80%.