Network theory posits that mental health problems arise from causal interactions among psychopathological symptoms. Through activation, spreading, and self-sustaining, symptoms gradually form closely connected networks, which is a core mechanism in the onset and development of mental health problems. Adolescence is a critical period for this process. Although previous studies have used longitudinal network analysis to examine temporal associations among psychopathological symptoms, individual differences in their severity are often overlooked, limiting a comprehensive understanding of heterogeneity in network dynamics. This study utilized group-based multi-trajectory modeling (GBMT) and cross-lagged panel network analysis (CLPN) to explore the structural characteristics, longitudinal associations, and core symptoms of adolescent psychopathological networks across different developmental trajectories. A total of 9653 fifth-grade students (49.7% female; Mage = 10.14 ± 0.36 years) from Beijing completed self-reported measures of depression, anxiety, and problematic smartphone use across four annual waves. Results showed that (1) Three developmental trajectories of mental health problems were identified: "Normal Group" (34.5%), "Potential Risk Group" (50.4%), and "High-Risk Group" (14.9%); (2) Symptom network structures differed across these groups: the Normal Group showed a stable dormant network with low connectivity, the Potential Risk Group exhibited a transitional active network with moderate connectivity, and the High-Risk Group demonstrated a stable active network with strong connectivity; (3) Core symptoms also varied across developmental trajectories and stages: in the Potential Risk Group, "Painful", "Interpersonal complaints" and "Loss of control2" predicted other symptoms most, while "Nomophobia", "Excessive use" and "Performance worry" were most predicted by other symptoms; in the High-Risk Group, "Worthlessness/guilt", "Habitual excessive use" and "Loss of control1" predicted other symptoms most, while "Nomophobia" was consistently most predicted by other symptoms. These findings enhance understanding of symptom spreading and maintenance in the dynamics of adolescent mental health problems, offering insights into comorbidity, precise risk identification, and targeted prevention strategies.