Objective: To investigate the effect of online and offline mindfulness training on improving anxiety and depression and sleep quality of college students,and to provide a reference for mental health promotion among college students. Methods: From October 2020, a total of 1 203 university students from North China University of Technology were screened with the Self rating Anxiety Scale (SAS), Self rating Depression Scale (SDS) and Pittsburg Sleep Quality Index (PSQI) using the whole group radom cluster sampling method. Totally 103 students who met the inclusion criteria were randomly divided into 64 online and 39 offline groups. The degree of improvement in anxiety, depression and sleep quality was assessed after the intervention. Results: The SAS, SDS and PSQI scores of college students after the online and offline the mindfulness training intervention significantly decreased compared with score before the intervention( t =5.57, 5.31, 3.99; 4.88,5.02, 5.88, P <0.01). The difference in the degree of improvement in sleep quality between the two interventions, online and offline, was statistically significant ( t =-2.55， P <0.05). The less the three symptoms of anxiety, depression and sleep were combined in university students, the higher the symptom remission rate of the positive mindfulness training (25% remission rate for all three symptoms together, 40% remission rate for two symptoms together and 100% remission rate for only one symptom). Conclusion Both online and mindfulness training can be used as an effective intervention for sleep, anxiety and depression; offline mindfulness training is more effective than online in improving sleep quality in university students; mindfulness training is more effective in relieving single symptoms.