Since the outbreak of COVID-19 in 2019, many countries have taken measures such as controlling the flow of people, logistics and reducing crowds. Educational institutions have shifted from traditional face-to-face teaching to online teaching. In order to understand the fatigue caused by long-term online teaching and its influence on teaching quality, this paper puts forward the concept of "student fatigue" according to the learning characteristics of students in our education system, and applies statistical principles to compile the student Fatigue Scale-18. In the four seasons of spring, summer, autumn and winter, 1236 times of 319 college students in grade 2021 were tested for fatigue, and the average incidence of fatigue was 64.97%. The incidence of fatigue in boys is higher than that in girls. There was a slight difference in the incidence of fatigue in different seasons, but no statistical significance was there. The effect of fatigue on online teaching is empirically analyzed. The degree of fatigue is negatively correlated with test scores. Students with better learning foundations are less affected by fatigue, while girls' scores are less affected by fatigue. This paper analyzes the common causes of students' fatigue, combined with the current research status of students' fatigue at home and abroad, and puts forward that college education should pay attention to students' fatigue, regularly or irregularly monitor students' fatigue, so that the incidence of fatigue is controlled below 30%. The analysis revealed that the degree of fatigue and gender significantly influenced academic performance. A negative correlation was found between fatigue degree and academic performance, indicating that more severe fatigue led to poorer academic results. Boys were more affected by fatigue than girls. The relationship between academic performance and seasons showed no significant impact. Try to avoid severe fatigue. In order to reduce the impact of fatigue on students' study and health, preventive measures should be taken. It provides theoretical and empirical basis for preventing students' fatigue, improving teaching quality and ensuring students' health.