Recently, the effect of a more efficient brief mindfulness training on the mental state, sports performance, and executive function has been explored. However, there are still very few studies, and the results are inconsistent. In the field of cognitive neuroscience, there is no research to observe the impact of brain nerve potential following a brief mindfulness training in athletes. Therefore, the purpose of this study was to explore the effects of a brief mindfulness training on sports performance, executive function, and even-related potential (ERP). And further observed whether executive function was a mediating factor for a brief mindfulness training to improve sports performance. This study recruited 45 track and field athletes, using within-subject and counterbalance design. To introduce mindfulness or relaxation training to athletes and fill in the trait scale before the formal experiment. Afterwards, the athletes need to go to the laboratory three times for 30 minutes of mindfulness training condition, 30 minutes of relaxation training condition, and 30 minutes of control condition. In addition, stress situations were added during the experiment. The exercise-related mental state scales were filled out before and after the three intervention conditions, and the executive function, ERP, and sports performance were measured after the intervention. The executive function was measured by the Stroop Test, and the sports performance was based on endurance performance by the Bruce test. In statistical analysis, this study observed the effects of three interventional situations on endurance performance of exhaustion time and maximal oxygen uptake using the repeated measured one-way ANOVA. Using repeated measured two-way ANOVA to observe the effects of three interventional situations on the exercise-related mental state scales, the reaction time and accuracy of Stroop test, and the amplitude of N2 and P3 of ERP. Finally, use the four-step method to observe whether executive function is a potential mechanism for a brief mindfulness training to promote endurance performance. The results showed that in sports-related mental states, a brief mindfulness training can significantly increase the level of state mindfulness, while both mindfulness and relaxation training can reduce negative emotions. In terms of endurance performance, the exhaustion time after the mindfulness training was longer than the relaxation training and control. In addition, in the reaction time of the Stroop test, the mindfulness training was faster than the relaxation training and control. Finally, the P3 amplitude after the mindfulness training was greater than the relaxation training and control in the ERP. This study preliminarily establishes that a brief mindfulness training is beneficial to the state of mindfulness, negative emotions, endurance performance, executive function, and ERP under stress. The benefits of negative emotions are also found in a brief relaxation training. Based o
