Objective: To explore the causal relationship between academic procrastination, negative emotions, self control, and smartphone addiction among college students, so as to provide theoretical reference for promoting their mental health and academic achievement. Methods: A multi stage cluster random sampling method was used to select 452 first year students from a university in Guangzhou as the research subjects. Procrastination Assessment Scale- Student (PASS), The Depression Anxiety Stress Scale (DASS-21), Self Control Scale, and Short Version of the Smartphone Addiction Scale (SAS-SV) were used as measurement tools. Three questionnaire surveys were completed in October 2024 (T1), February 2025 (T2), and May 2025 (T3). Coss lagged models were utilized to analyze the causal relationship between academic procrastination, negative emotions, self control, and smartphone addiction. Results: The SAS-SV scale for college students showed an average score of (40.52±1.96), with 43.1% of freshmen exhibiting smartphone addiction.Positive correlations were observed between academic procrastination, negative emotions, and smartphone addiction across different time points, while self control exhibited negative correlations with these three variables ( r = 0.30 -0.62, -0.72 to -0.34, all P <0.05). Cross lagged model results indicated that academic procrastination and negative emotions at T1 and T2 positively predicted smartphone addiction at T2 and T3 (T1→T2, β =0.22, 0.35; T2→T3, β =0.21, 0.24; all P < 0.05 ). Self control negatively predicted smartphone addiction (T1→T2, β =-0.32; T2→T3, β =-0.26; both P <0.05). In reverse causality regression models, smartphone addiction at T1 and T2 positively predicted academic procrastination and negative emotions at T2 and T3 (T1→T2, β =0.09, 0.24; T2→T3, β =0.10, 0.35; all P <0.05), but no statistically significant predictions were found for self control (T1→T2, β =-0.04; T2→T3, β =-0.03; both P >0.05). Conclusion Academic procrastination and negative emotions exhibit bidirectional causality with smartphone addiction among college students, while self control unidirectionally predicts smartphone addiction.