Provided in the present invention is a method for measuring free bismuth in colloidal bismuth pectin or in a preparation containing colloidal bismuth pectin, comprising: adding an ethanol aqueous solution having a volume concentration of 7-20% in colloidal bismuth pectin or in a preparation containing colloidal bismuth pectin, and shaking to dissolve evenly, or adding an ethanol aqueous solution which has a volume concentration that does not exceed 5% and shaking to disperse； then adding ethanol to the dispersion liquid such that the ethanol volume concentration is 30-50%, and shaking to dissolve evenly so as to obtain a colloidal solution； and centrifuging to extract a supernatant so as to measure by means of a complex titration method or ultraviolet spectrophotometry and calculate the content of free bismuth in the colloidal bismuth pectin or in the preparation containing colloidal bismuth pectin. The ethanol aqueous solution not only has good solubility for free bismuth, but also may block colloidal bismuth pectin molecules to a certain extent, and effectively prevents the dynamic release of bismuth salt from colloidal bismuth pectin. The present invention uses an ethanol aqueous solution to disperse the colloidal bismuth pectin to measure free bismuth, and the measurement result of free bismuth is more accurate and reliable.
