Asthma is a common respiratory disease in children. Family factors play a role in its incidence and severity. This study investigated the effect of parental psychological flexibility, parental psychological adjustment to the child's illness, and parental psychological distress on the severity of asthma symptoms of children through mediating child anxiety. A total of 216 parents of children with asthma were asked to complete the Acceptance and Action Questionnaire, the Parent Experience of Child Illness, the Depression, Anxiety and Stress Scale - 21 Items, and the parent-report Spence Children's Anxiety Scale. Severity of asthma symptoms was assessed by spirometry. The highest path coefficient was between parental psychological flexibility and the severity of paediatric asthma symptoms (β = 0.34). Parental psychological distress was found to affect the severity of asthma symptoms of children (β = -0.21) and also mediate child anxiety and then affect the severity of asthma symptoms of children (β = -0.25). Parental psychological flexibility, parental psychological adjustment to the child's illness, and parental psychological distress had significant effects on the severity of asthma symptoms of children through mediating child anxiety.