BACKGROUND: In order to gain a deepened understanding of the impact of public health emergency and to develop effective interventions and preventions, this study aimed to evaluate risk and protective factors associated with anxiety in children and adolescents and to explore potential moderators in the background of COVID-19 within the framework of socio-ecological model. METHODS: A literature search was conducted in Web of Science, MEDLINE, PubMed, Scopus, EBSCO, ScienceDirect, Emerald, and CNKI for studies published from early 2020 to early 2023 that examined factors associated with anxiety among children and adolescents with age range of 6 to 17 years old. Random effects models and a three-level meta-analytic approach were used. RESULTS: In total, 141 articles and 1,018,171 subjects were included, with 1002 effect sizes extracted. 32 protective factors and 48 risk factors were examined, yielding significance for 14 protective factors and 29 risk factors, including individual factors (e.g., gender, logOR = -0.37, 95 % CI [-0.47, -0.27], p <
0.001
age, logOR = -0.12, 95 % CI [-0.22, -0.02], p = 0.02
emotional functioning, logOR = -1.45, 95 % CI [-1.84, -1.05], p <
0.001
pre-existing condition logOR = 0.94, 95 % CI [0.58, 1.30], p <
0.001
electronic device or internet addiction, logOR = 1.81, 95 % CI [0.74, 2.88], p <
0.001), family factors (e.g., family socioeconomic status, logOR = -0.25, 95 % CI [-0.39, -0.10], p <
0.001
family functioning, logOR = -1.31, 95 % CI [-1.60, -1.02], p <
0.001
anxiety level of caregiver, logOR = 1.06, 95 % CI [0.75, 1.37], p <
0.001), community factors (e.g., overall social support, logOR = -0.93, 95 % CI [-1.84, -1.05], p <
0.001
school burden, logOR = 0.56, 95 % CI [0.21, 0.90], p = 0.002), and COVID-19-related factors (e.g., higher exposure risk in local community or city, logOR = 0.48, 95 % CI [0.17, 0.78], p = 0.002
distant learning, logOR = 0.73, 95 % CI [0.19, 1.28], p = 0.008
COVID-19-related distress, logOR = 1.42, 95 % CI [0.55, 2.29], p = 0.001
). The majority of studies showed no publication bias. Age group moderated the relationship between gender and level of anxiety (F (1,96) = 4.42, p = 0.038), and no other moderator showed significance. LIMITATIONS: This study does not reveal causality but correlation in nature, and our findings should be interpretated with caution. CONCLUSIONS: Public health emergencies could bring challenges to the mental health of children and adolescents. Prevention and intervention strategies for children and adolescents with high risks, and family-based and community-based programs should be encouraged to buffer the adverse impact on children and adolescents. This study has been prospectively registered at PROSPERO (registration number: CRD42022316746).