The invention discloses a method for preparing adsorbent with improved adsorption capacity by printing waste liquid extract. The method comprises the following steps: adding a chemical agent capable of generating hydrogen ions to the printing waste liquid, performing a stirring reaction, and performing condensation on an extractable substance in the waste liquid to obtain insoluble fine solid particles; continuously stirring the materials, slowly adding a chemical agent which reacts with the waste liquid to form microbubbles into the waste liquid, and forming a three-phase contact interface ofgas, liquid and solid among the solid particles for preventing flocculation; stopping stirring, heating the materials until temperature is 5 to 30 DEG C higher than a softening point of an aqueous polymer organic matter, and forming a large particle solid extract by heat effect; performing insulation, and forming a blocky extract with developed pores; fully shrinking a volume of the blocky extract, draining water, cooling the material with a saturated potassium hydroxide solution and soaking the material; taking out the blocky extract, cooling the material, and drying the material; and performing one-step charing and activating on the dried extract at the temperature of 700 DEG C under nitrogen protection for 1-4h to obtain the adsorbent. The adsorption capacity of the adsorbent is improved.