Objective To explore the time of application of hemoperfusion (HP) for the treatment of acute serious organophosphorus pesticide (ASOPP). Methods One hundred and four patients with ASOPP were randomly divided into two groups, 46 patients accepted traditional treatment(control group), 58 patients were treated with traditional treatment and HP (HP group). The patients in HP group were again divided into three groups according the different time of treatment (time of beginning HP after poisoning), the 4-8 hours group (HP-1 group, 27 patients), the 9-16 hours group (HP-2 group, 19 patients), the 17-32 hours group (HP-3 group, 12 pafients).Tbe coma period, the dosage of atropine, the time of regaining the vitality of cholinesterase, the time of hospitalization and the rate of fatality and curing among groups were observed. Results The coma period, the dosage of atropine, the time of regaining the vitality of cholinesterase, the time of hospitalization and the rate of fatality of the HP group were less than those of the control group (P<0.05). Compared with HP-1 group, the eoma period, the dosage of atropine, the time of regaining the vitality of eholinesterase and the time of hospitalization of the HP-2 group and the HP-3 group were higher (P<0.05), but the difference of the rate of fatality and curing between the HP-1 group and the other HP groups was not statistically significant (P>0.05). The difference of all of the above indicators between HP-2 group and HP-3 group was not statistically significant (P>0.05). Conclusion Application of hemoperfusion among 4-32 hours after poisoning for the treatment of ASOPP can improve the efficacy of therapy, and the efficacy of application of hemoperfusion among 4-8 hours is the best.