The invention discloses a method for preparing active dye, namely active deep-red C-D by utilization of a
microreactor, comprising the following steps that: J acids are coupled with diazonium salts of ethyl
sulfone sulfate ester
aniline compounds which contain sulfonic group, methyl, methoxyl group,
ethyl group or oxyethyl group, and then active deep-red C-D azo dye is obtained; the
coupling temperature is between10 and 25 DEG C and the pH value is equal to 1.5 - 6.5; the
microreactor is adopted during the reaction process; a plurality of parallelly connected microchannels with
diameter of between 10 and 500 micrometers are arranged inside the
microreactor and both ends of the microchannels have shell covers. The product has good vividness, stable performance, good
reproduction quality, high dye yield, good deep
dyeing property and high fixation rate. The
structural formula of the active deep-red C-D is as above, wherein, R1 and R2 are equal to H, SO3H, CH3, OCH3, OC2H5 and C2H5.