In the present study, chitin isolated from locally available shrimp shells was pulverized to obtain three different particle sizes and then deacetylated to obtain various deacetylation degrees and molecular weights of chitosan. In the batch mode experiment, the removal efficiency of heavy metals [Zn(II), Cd(II), Pb(II), and Cu(II)] from synthetic wastewater solutions with different concentrations ranging from 10-30 mg/l using three molecular weights chitosan was evaluated. Cadmium was the best metal chelated by all three types of chitosan and the extent of adsorption was considerably higher in the type 1 of chitosan sample of small particle size with lower of molecular weight and higher of degree of deacetylation compared with types 2 and 3 chitosans. In addition, the maximum percent removal of heavy metal ions was at concentration 10 and 20 mg/l in order of Cd (II > Pb (II) > Cu (II) )> Zn (II), while at concentration 30 mg/l the removal efficiency of chitosan was in order of Cd (II) > Cu (II) > Pb (II) > Zn (II). The influence of pH is presented and the maximum uptake of metal ions was obtained at pH 4.0 at room temperature.