Heavy metal chelator compound containing chitosan derivative

The present invention provides a heavy metal chelator composition containing chitosan derivative. The composition contains 1-100 wt% of chitosan derivative with at least one dithioformic acid radical and 0-99 wt% of polyamine derivative with at least one dithioformic acid radical. The heavy metal chelator composition is applicable to treatment of waste water and sludge containing heavy metal ions, refuse incineration flyash or soil contaminated by heavy metal ions.