Objective: To evaluate the effect of online objective structured clinical examination (OSCE) in critical care teaching. Methods: This is a self-controlled prospective study performed in Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College from 2020 to 2021. Consecutive students came from various surgical departments. Online tests were conducted for each student pre-and post-ICU round. There were three spots in online OSCE including clinical case, electrocardiography and chest X-ray. Results: Twenty-four students completed the tests. The median age is 27 years (24–28) in the cohort. There are 18 males and 6 females. Of twenty-four students, 7 came from department of neurologic or head-neck surgery, 3 from department of thoracic surgery, 12 from department of abdominal surgery, and 2 from others. There was significant difference in scores between pre-round and post-round ICU test in the chest X-ray spot, which was 3.33±4.81 and 6.67±4.81 respectively (P = 0.029). Scores in the postround ICU test in the electrocardiography spot was higher than that in the pre-round test (5.85±5.05 vs. 8.33±3.80)however no significance was reached (P = 0.056). There was no significant difference in the scores between pre-round and post-round ICU test in the clinical case spot (63.33±18.33 vs 71.67 ± 13.07, P = 0.116). Lastly, there were significant differences in total scores between pre-round and post-round ICU test (72.50±19.83 vs 86.67±13.40, P = 0.019). Conclusions: Online OSCE was feasible in the teaching evaluation of surgical rotation residents in ICU. Surgery rotation residents in ICU should receive more training in electrocardiography and chest X-ray.