Online learning as an emerging learning method has a significant impact on education, which cannot be ignored. This article explores the relationship between engagement (including cognition, behavior and emotion), motivation, environment, and college students' concentration in online learning during the COVID-19 pandemic. A total of 889 college students from 6 universities in Western China were sampled using cluster sampling. By constructing a hierarchical linear regression analysis, the study investigated the impact and pathways of cognition, behavior, emotion, motivation and environment on concentration. The results showed that there is a significant positive correlation and impact between engagement, motivation, environment, and concentration. Among the factors of engagement, cognition has the greatest impact on concentration, followed by motivation, emotion, behavior, and finally environment. Among these influencing factors, internal factors including cognition, motivation, emotion, and behavior play a primary role, while external factors such as environment play a secondary role. There are certain differences in concentration among students from different genders, grades, majors and school levels. This study further clarifies the factors affecting the concentration of Chinese college students in online learning, which is of great significance to the improvement of online learning theories and the exploration of practical reforms. Students of different genders, grades, majors, and school levels exhibit certain differences in their levels of concentration.