Abstract: To study the mordant dyeing mechanism with metallic ion mordant agents when dyeing is carried out with natural dyes,mordants containing metal ions such as titanium,iron,aluminum and zinc was applied onto the cotton fabric before it was dyed with natural dye — carminic acid.The dye-uptake,shade,and brightness of the dyed cotton fabric varied with different mordants and they exhibited certain changes when compared with non-premordanting counterpart.Mordant dyeing rendered the fabric better fastness and made the mechanical properties change;apparatus analysis showed that after mordanting with metallic ions,the surface of fabric is eroded slightly and the fixture can be seen apparently on the surface of fabric treated with Ti ion;the coordination reaction between metallic ions and coordination group on the fiber mainly acts on the amorphous area of fabric.