The adsorbent was prepared from corn stalk carbon by using H3PO4 as activating agent and fluorescein was used as adsorbate. The paper studied the influence factors of adsorption ability of ACF and the adsorption mechanism. The results showed that when the carbonization temperature is 750℃,the dosage is 0.2g; the pH is 3, ACF has stronger adsorption ability on fluorescein. ACF can adsorb low concentration fluorescein better, and Langmuir isotherm can well describe the adsorption characteristic, and the value of adsorption intensity factor (a) is positive, which indicates that the adsorption process has spontaneity, the maximum amounts of ACF adsorbing fluorescein is 19.608 mg/g. The adsorption behavior reached saturated after 8h, by substituting experimental data into kinetics models, quasi-second-order kinetics model could better describe the kinetics of ACF adsorbing fluorescein. Experimental results and adsorption mechanism showed that ACF can effectively treat wastewater containing fluorescein. This research discussed the process of ACF adsorbing fluorescein from the aspects of impact factor, adsorption kinetics and thermodynamics so as to provide theoretical basis for the treatment of dye wastewater by adsorption method.