Disperse dyes having different molecular structures were prepared and their dyeing properties on PU, PET and PU-coated PET were studied. A disperse dye with common structure showed faster absorption rate into PU for its high affinity to PU at low temperature and this resulted in faster dyeing rate on PU-coated PET than on PET. On the other hand, a disperse dye having bulky structure was adsorbed into both PU-coated PET and PET at similar rate and it showed little affinity to PU in the whole dyeing temperature range. The amounts of disperse dyes eliminated from substrates by reduction clearing and washing fastness test were also measured. It was found that the disperse dye with bulky structure slipped out of PU in reduction clearing and washing fastness test in smaller quantity than the disperse dye with common structure. This phenomenon was corresponding well with the result of washing fastness test.