This study examined the determinants of happiness for preschoolers from a developmental-psychological perspective and a ecological-contextual perspective. The results suggest that the determinants of happiness for preschoolers include both the developmental factors like control of emotions, stress coping skills, social competency, subjective health, developmental level and the ecological context like their families, educational institues, schools, extracurricular activities, religious groups, hospitals, local communities, parent's occupations, culture and traditions and politics and polices.