Abstract: Objective To explore influences of smartphone addiction and negative affect on sleep quality among university students and to provide evidences for improving sleep quality and promoting mental and psychical health in the students.Methods A total of 770 university students were surveyed with Pittsburgh Sleep Quality Index, Smartphone Addiction Scale, and Positive and Negative Affect Scale.Results Among the students, the average score was 5.13±2.16 for sleep quality, 36.94±8.28 for smartphone addiction, and 20.80±5.99 for negative affect, respectively;and the detection rate of sleeping problems was 15.8%.Statistically significant variations were observed in the scores of daily-life disturbance, smartphone withdrawal symptom, smartphone overuse, tolerance, overall smartphone addiction, and negative affect among the students with different sleep quality(all P<0.01).Sleep quality was partly associated with smartphone addiction and negative affect in the students(both P<0.05).Negative affect had both direct effect(regression coefficient=0.43) and indirect effect(regression coefficient=0.04) through smartphone addiction on sleep quality;smartphone addiction and negative affect had a total effect on sleep quality of 0.58.Conclusion Smartphone addiction and negative affect influence sleep quality and smartphone addiction prevention and mood control could improve sleep quality among university students.