BACKGROUND: This study aimed to compare the relevant clinical parameters of neonates with MAS who are supported by proportion assisted ventilation (PAV) and synchronized intermittent mandatory ventilation (SIMV). METHODS: Forty neonates diagnosed as MAS who required mechanical ventilation were divided randomly into PAV group and SIMV group (N.=20). The respiratory rate (RR), heart rate (HR), peak inspiratory pressure (PIP), mean arterial blood pressure (MABP), arterial-to-alveolar oxygen tension ratio (a/APO(2)), fraction of inspiration oxygen (FiO(2)), mean airway pressure (MAP) and tidal volume (VT) were measured before the ventilation, 1,12, 24, 48 hours after the ventilation and before weaning. RESULTS: We observed no significant differences in the mechanical ventilation time, oxygen supply time, hospital stay between PAV and SIMV groups. In addition, we found no significant differences in HR, MABP, a/APO(2) and FiO(2) at every time point between two groups (P>0.05). However, we observed significant differences in RR, MAP, PIP and VT at every time point between two groups (P<0.05). CONCLUSIONS: PAV and SIMV might be a useful ventilator mode to support the neonates with MAS who require ventilation. To achieve the same effect, PAV adopts rapid shallow breathing pattern, with smaller tidal volume and lower MAP and PIP.