This is a quasi-experimental study was done to investigate the impact of developmental care on length of mechanical ventilation on 60 inpatient neonates who undergo mechanical ventilation at 4 hospital affiliated to Shahid Beheshti University of Medical Sciences. A convenience sample was selected from 4 hospital in Tehran, Iran that nonrandomly assigned to interventinal from Mahdieh Hospital (n=30) and control group (n=30) from other 3 hospital (Mofid Childrenʼs Hospital, Imam Hossein Hospital and Shohada Tajrish Hospital). Inclusion criteria: gestational age less than 33 weeks with birth weight equal or less than 2500 g; neonates suffered from respiratory distress syndrome; mechanical ventilation> 24 hours of first 48 hours of life and exclusion criteria: treatment with surfactant, congenital anomalies; asphyxia; respiratory disorders; cyanotic heart disease; mouth and facial abnormalities; maternal use of opium drugs during pregnancy; neonatal death; intraventricular hemorrhage (grade 3 or 4 ) alongside hydrocephalus; sepsis, necrotizing enterocolitis; growth disorders; bronchopulmonary dysplasia; patent ductus arteriosus requiring treatment; pneumonia caused by mechanical ventilation. Data collection included demographic information that completed under supervision of researchers in the hospitals for intervention groups. Developmental care intervention consist of: change the position every 2-3 hours, hand near face, nesting, Right side or prone position to improve gastric emptying and reduce the effects of gastroesophageal reflux, non-nutritive sucking before invasive intervention and gavage, Using gentle and quiet handling techniques, trunk flexion, shoulder and hip flexion and adduction, prevent suddenly change position and Keep hands of care keeper over the baby's head before beginning any care for providing the infant's sense of care. Care in the intervention group was maintained until the end of the need for mechanical ventilation. Daily nursing care for infants in the control group was conducted.