Objective To investigate the effect of mechanical ventilation in acute organophosphorous pesticide poisoning(AOPP) with respiratry failure. Methods Forty from forty-two AOPP patients with respiratry failure were treated with mechanical ventilation(MV) ,gastrolavage and other methods. Five minutes before mechanical ventilation and two hours after mechanical ventilation, patients' heart rate (HR), systolic blood pressure (SBP), arterial partial blood pH, oxygenation index, the pressure of carbon dioxide (PaCO2) were compared. Results Patients' HR was increased ( P＜0. 05 ), SBP was increased ( P＜0. 01 ), arterial partial blood pH was increased( P＜0. 01 ), oxygenation index was increased(P＜0. 01 ) ,PaCO2 was decreased(P＜0.01 ). Thirty nine cases were cured,three cases dided. Conclusion Mechanical ventilation can effectively treat the AOPP patients with respiratry failure.