Objective: To understand the vitamin D nutritional status and associated factors of children and adolescents aged 6-18 in Yinchuan, so as to provide theoretical basis for improving the vitamin D malnutrition status of children and adolescents. Methods: Using stratified cluster sampling method, 1 615 children and adolescents from 36 classes in 2 primary schools, junior high schools and high schools were randomly selected from Yinchuan, Ningxia. Venous blood sampling,physical examinations and questionnaires were conducted. Results: The vitamin D deficiency rate and appropriate rate for students were 66.9% and 33.1%, respectively. There was a statistically significant difference in vitamin D deficiency among different age groups(χ2=25.65, P<0.05). The 6-year-old group had the highest(79.2%), followed by the 13-year-old group (76.6%), and the 12-year-old group (75.3%). The results of binary Logistic regression showed that the factors influencing the vitamin D nutritional status of children and adolescents included age(OR=0.95), daily outdoor exercise time(OR=0.49), exclusive breastfeeding (OR=0.63) and mother’s education(OR=0.73, 0.43). The decision tree QUEST and Logistic regression combination model results show that the key factors affecting vitamin D nutrition status include daily outdoor exercise time, age, mother’s education, BMI, and interaction between outdoor exercise time and age, interaction between outdoor exercise time and mother’s education, interaction between age and mother’s education, interaction between exclusive breastfeeding and BMI. Conclusion The detection rate of vitamin D deficiency in children and adolescents aged 6-18 in Yinchuan is high, factors associated with vitamin D nutritional status includes daily outdoor exercise time, age, mother’s education, BMI, and interaction between outdoor exercise time and age, interaction between outdoor exercise time and mother’s education, interaction between age and mother’s education, interaction between exclusive breastfeeding and BMI.