To investigate the effect and mechanism of microRNA-146a (miR-146a) on Toll-Like Receptor 4 (TLR4) inflammatory signal pathway in the lung tissues of rats with mechanical ventilator-induced lung injury. Thirty-two healthy male Sprague-Dawley rats were randomly divided into 4 groups ( =8 each): group A, normal control group, no mechanical ventilation, spontaneous breathing; group B, mechanical ventilation injury; group C, mechanical ventilation injury plus no-load virus transfection; group D, mechanical ventilation injury plus virus transfection; in group B, C, and D, mechanical ventilation were performed, respiratory rate was controlled at 80 beats/min, tidal volume was 40 ml/kg, inhaled oxygen concentration (FiO ) was 21%, inhalation/expiration ratio was 1∶2, positive end expiratory pressure ventilation (PEEP) was 0, each group were ventilated 4 hours daily, 7 days continuously to establish ventilator induced lung injury (VILI) rat model. Paraffin-embedded sections of lung tissue were stained with HE, the mo