Inclusion Criteria:  Preterm infants gestational age (GA) > 28 weeks and < 37 weeks, and birth weight less than 2200 grams; The main caregiver of the preterm infants can communicate in Mandarin and Taiwanese; The parents of the preterm infants and their main caregivers agrees to participate in this research and signs the research consent form  Exclusion Criteria:  Premature infant is diagnosed with limb dysfunction or brain neuropathy, such as: third or fourth degree intraventricular hemorrhage or peripheral ventricular leukomalacia; Other diseases that affect sleep, such as: congenital nerve development Abnormalities, epilepsy; Those who need to take muscle relaxants, sedatives or bronchodilators