Background: Humic substances in drinking water react with chlorine and form carcinogenic compounds. The adsorption process, as a simple and cost-effective process, has attracted great attention in pollutant removal. The aim of this research was kinetic and isotherm study of humic acid adsorption by silicon nanoparticles in water. Methods: This experimental study was conducted on a synthetic and then a real water sample collected from Alavian Dam in Maragheh city. The effects of pH, absorbent amount and time on the removal of humic acid were evaluated. In order to get a better insight into the process of adsorption, the adsorption kinetic and equilibrium isotherm and thermal energy were determined. Data analysis was performed through SPSS16 and using regression and Pearson coefficient of correlation. Results: The highest percentage of Humic acid adsorption was observed at pH=4, retention time of 10 minutes and absorbent amount of 0.25 g/L with removal efficiency of 88.4% and 86.7% for synthetic and real samples respectively. Meanwhile, the removal of humic acid followed Langmuir isotherm and its rate followed the second order kinetic model. Optimal capacity of adsorbent was 1.56 mg/g based on Langmuir model. The obtained RL (0.1) shows efficient silicon nanoparticles adsortion capacity in humic acid removal. Thermodynamic study showed that humic acid adsorption on silicon nanoparticle is a spontaneous and thermal process. Conclusion: The adsoption of humic acid by nanoparticles depends on the initial concentration of the compounds and as the initial concentration increases the adsorption time decreases. This is an appropriate method for eliminating humic acid.