The invention relates to a new application of low molecular citrus pectin, in particular to the application of low molecular citrus pectin for treating and preventing lead and heavy metal poisoning in prepared medicines, foods and health care products. The low molecular citrus pectin is a compound prepared from soluble dietary fiber and galacturonic acid, the polysaccharide derivative is used as a metal ion absorbent (chelating agent), has absorption action on heavy metal ions, can remove heavy ions, such as Zn2+, Cu2+, Cd2+, Ag+, Cr3+, Ni2+, Hg2+, Pb2+ and the like. The low molecular citrus pectin is different from common chemical chelating agents; proved by animal and clinic experiments, lead, mercury and arsenic are discharged out of human bodies during toxin discharge, and the key level of calcium, magnesium, zinc or other minerals can not be influenced. The natural chelating function of the low molecular citrus pectin is a most ideal and successful solution for heavy metal pollution in the human body at present. Thus, the low molecular citrus pectin has the function of preventing various diseases and especially has special functions of clearing away harmful cells and discharging toxins in the human body.