The ester type disperse dyes are easily hydrolyzed in alkali medium. their hydrophobic properties have influence on thermomigration on polyester, acetate, cotton, and wool. Thermomigration is recently reported to be the most important factor, governing the perspiration and wash fastness of polyester/cotton blends. The aim of this study is to synthesize alkali clearable disperse dyes containing ester group in the diazo components with alkyl group of various chain length. Alkali clearable azodisperse dyes were synthesized using 4-amino-3-nitroalkylbenzonate(R: methyl, ethyl, and butyl) as diazo component and N, N-diethylaniline as coupling component. After they were applied on polyester and polyester/cotton blends, effects of hydrophobic properties on thermomigration were investigated. The chain length of alkyl group in the diazo component is suposed to control the hydrophobic properties of disperse dyes.