Four photocolorimetric methods have been comparatively studied for determining soluble silicon in freshwater. Meanwhile, the effects of glass containers on the determination and the interference of the phosphate ion on chromogenesis were also investigated. It was demonstrated that 1, 2, 4-trichlorobenzene amino phenol sulfonic acid reduction-silicon molybdenum blue method is highly sensitive and accurate for the determination of soluble silicon in fresh water, and has an optimal concentration range from 0.05-20 mg/L. Ascorbic acid reduction-silicon molybdenum blue method and metol reduction-silicon molybdenum blue method are highly sensitive but less accurate; silicon molybdenum yellow method is simple in operation but with low sensitivity. Glass containers used do not influence the determination by the four methods, and the interference of phosphate ion could be eliminated.