Objective: To explore the association between daytime light exposure intensity and duration and objectively assessed sleep parameters among primary school students, so as to provide a scientific basis for understanding the impact of light exposure on children s sleep quality. Methods: From October 2023 to May 2024, a total of 741 primary school students in grades 2 to 3 were recruited from two primary schools in Chuzhou City, Anhui Province. Participants were required to wear an illuminance meter and an actigraph concurrently for 5 consecutive days to simultaneously collect 24 hour light exposure, sleep parameters, and physical activity data. Objective sleep parameters included total sleep time, sleep efficiency, sleep onset latency, wake after sleep onset, and sleep fragmentation index. Generalized linear model was applied to analyze the associations of average daytime (overall, morning, afternoon) light exposure intensity and exposure duration at different illuminance thresholds with various sleep parameters among primary school students. Results: The mean values of total sleep duration, sleep efficiency, sleep latency, wake time after sleep onset and sleep fragmentation index were (465.70±40.27)min, (83.22±5.16)%, (17.40±8.31)min, (75.97±26.81)min and (26.23±6.20), respectively. Generalized linear model showed that the average daytime light exposure intensity and duration of exposure ≥1 000 lx were positively correlated only with total sleep duration ( β =0.94, 8.51, both P <0.05). Morning light exposure intensity was associated with higher sleep efficiency ( β =0.11), longer total sleep duration ( β =0.80), shorter sleep latency ( β = -0.20 ), shorter wake time after sleep onset ( β =-0.57) and lower sleep fragmentation index ( β =-0.11) (all P <0.05). The duration of morning light exposure at ≥1 000 lx also improved childrens sleep efficiency, total sleep duration, sleep onset latency, wake time after sleep onset and sleep fragmentation index ( β =1.74, 13.91, -4.43, -11.04, -2.01, all P <0.05). Conclusions There is a significant association between morning light exposure intensity, exposure duration ≥1 000 lx, and multiple objective sleep parameters among primary school students. Increasing morning outdoor activities or high illuminance indoor light exposure could serve as feasible intervention strategies to improve the sleep of primary school students.