The content of fucoidan in seaweed can be determined by Dische colorimetry. It is a simple methods, easily operating without expensive equipment, and is safe and reliable. But the speed of the analysis is too slow. The effects of the shaking conditions, temperature and L-cysteine hydrochloride on the color stability were investigated in this study to improve the efficiency of the method. Verification methodology was applied by investigating the precision, color stability and spike and recovery. The experimental results show that the modified Dische colorimetry can greatly shorten color reaction time, and improve the precision, color stability, and spike and recovery are in accordance with the relevant regulations. The contents of fucoidan in different kind of seaweed were determined by the modified Dische colorimetry.