This study aims to find the correlation the low-molecule fucoidan for cancer prevention with an accelerated formation of cotinine. In the presence of fucoidan, a nicotine to cotinine coversion was studied in established assay, direct mixture method and Hep-G2 cell line method. Fucoidan of $1{mu}g/mL$ showed the potential effect for converting nicotine to cotinine in the direct mixture method compared to control. Increase of conversion rate at the treatment of fucoidan is exhibited as 15 times compared to control. In Hep-G2 cell treatment, fucoidan showed the potential activity for converting nicotine to cotinine as 6 times compared to control. Therefore, fucoidan was shown to be effective in the conversion of nicotine into cotinine even though it is not higher content of polyphenol and flavonoid than its of green tea extract.