OBJECTIVE: To explore the effect of delayed pre-job occupational health examination on occupational health surveillance by analyzing the results of pre-job occupational health examinations in radiation exposed workers. METHODS: A convenience sampling method was used to select 1 385 radiation workers as the research subjects in Guangdong Province in 2016 at a pre-job occupational health examination. Workers who did not engage in radiation work were selected as control group. Workers who engaged in radiation work but did not take pre-job occupational health examinations were selected as observation group. The difference of the results of occupational health examination between the two groups was analyzed. RESULTS: The proportion of the observation group was 55. 8%(773/1 385). The abnormal rates of the white blood cell( WBC) count,“double + ring”rate and lens in the observation group were higher than those in the control group(9. 3% vs 5. 7%,6. 0% vs 3. 6%,6. 2% vs 3. 6%,P < 0. 05),respectively. The WBC count in the observation group was lower than that in the control group [(6. 1 ± 1. 5) × 10~9/L vs(6. 7 ± 1. 5) × 10~9/L,P < 0. 01]. The contents of the thyroid stimulating hormone and triiodothyronine in the observation group were higher than those in the control group[(1. 3 ± 0. 4) m U/L vs(1. 2 ± 0. 3) m U/L,(1. 8 ± 0. 4) nmol/L vs(1. 7 ± 0. 5) nmol/L,P < 0. 01]. The tetraiodothyronine level in the observation group was lower than that in the control group [( 110. 8 ± 22. 4) nmol/L vs(113. 8 ± 23. 2) nmol/L,P < 0. 05]. CONCLUSION: The delay of pre-job occupational health examination of radiation exposed workers affects the examination results and the accuracy of basic health records.