A series of haloacetyl reactive dyes have been synthesised. The reactivity of haloacetyl groups and the dyeing properties of the dyes on silk fabric were studied. The results show that the bromoacetyl group is more reactive than the chloroacetyl group and molecules containing a bromoacetyl group would dye silk under relatively mild dyeing conditions. Both the exhaustion and fixation on silk fabric are increased if a second reactive group is present in the molecule