Background & Objectives: Textile wastewater is known as environmental pollutant. The main characteristic of textile wastewater is presence of non-used color and various organic or inorganic pollutants. Therefore it is necessary to be treated before discharging to the environment using effective methods. Methods: Pumice was obtained from Tikmeh Dash Region of East Azerbaijan and was treated by HCL for improvement of its adsorption capacity before using as an adsorbent. The morphology of the medium used was investigated by XRF and SEM technology. Removal of Acid Red 14 and Acid Red 18 was investigated as a function of initial dye solution and contact time. In addition, equilibrium data was fitted onto Langmuir and Freundlich isotherm model. Furthermore, experimental data was fitted onto three kinetic models. Results: Removal of both dyes was increased by increasing of contact time and initial dye solution. The results of linear regression analysis show that removal of Acid Red 14 and Acid Red 18 follow the Freundlich (r2>0.99) and Langmuir (r2>0.99) model, respectively. Adsorption capacity was 29.7 and 3.125 mg/g for Acid Red 18 and Acid Red 14, respectively. The fitting of experimental data onto kinetic models shows the best fitting of obtained data onto pseudo-second order for Acid Red 14 and Acid Red 18. Conclusion: The result of present work shows that the effective removal of two azo dyes occurs in pumice stone modified by HCL.