Reactive disperse dyes having acryloxyethyl group were synthesized and their dyeing and fastness properties were compared with disperse dyes. The K/S value of the reactive disperse dyes were similar to those of the disperse dyes on polyester fiber and were much higher on nylon fiber. When polyester and nylon fibers were dyed in a dye pot at the same time to simulate the condition of dyeing N/P union fabrics, the difference of K/S values between polyester and nylon fibers dyed with reactive disperse dyes were smaller than that with the fibers dyed with disperse dyes. The dyeing fastness properties of reactive disperse dyes were good.