With the rise of short videos platforms, such as TikTok, Instagram and Youtube, short-form videos have become an indispensable part of daily life. Although it has an extremely high transmission efficiency and due to it is entertainment it can provide people with a way to relax, academic community still hold the view that it may has negative impacts on cognitive competence. This essay aims to discuss how the duration of short video usage and addiction tendency influences the attention and cognitive function of university students, including duration allocation and watchfulness, and further analysis the impacts on scholastic attainment. This essay will adapt mixed research methods. Firstly, using questionnaire survey to analyses the correlation between duration of short video usage and academic performances, and then exam the relationship between Prefrontal Theta power and addiction tendency through electroencephalography technology (EEC) and attention net test. The results are that it shows that students who spend more than 3-4 hours watching short videos every day have significantly lower university GPA compared to those with lower usage levels. Besides according to EEG data, the greater the short-video addiction tendency, the lower the Prefrontal Theta power when they faced cognitive conflictions, and self-control ability will reduce. Overall, prolonged consumption of short videos can lead to "chronic dopamine depletion" and fragmented attention, thereby damaging the brain's executive control network. This neurological damage directly translates into poor academic performance.