PURPOSE: To obtain a reactive dye useful for dyeing and textile printing of natural and synthetic materials containing OH groups or amide groups by selecting a specified monoazo reactive dye.

CONSTITUTION: A monoazo dye in a free acid state expressed by formula I is selected. In formula I, R1 is H, CH3, CO2H, CH2SO3H, C6H5 or groups expressed by formula II and formula III; R2 is H, CH3, C2H5, CH2CH2SO3H, CH2CH2OSO3H or groups expressed by formulae II to V; R3 is a (substd.) 1-6C alkyl or aryl; R4 is H, a 1-6C alkyl or OR3.