Objective To observe the possible bias in Graybiel's scoring system caused by change of complexion and sweating for grading of motion sickness in hot-humid environment, so as to make improvement to the system. Methods A total of 567 subjects received Collis rotating chair tests in room temperature environment, hot temperature environment, and hot-humid environment. The severity of motion sickness was graded by Graybiel's scoring system. Paired design was done among 4 groups (calculated with pallor and sweating, no pallor, no sweating, and no pallor no sweating). Results Graybiel's scores were significantly different under 3 different environments, either calculated with pallor and sweating, or without pallor, without sweating, or without both (P<0.01). The corresponding grades of Graybiel's score were also significantly different when calculated without sweating and without both pallor and sweating, but not when calculated without pallor. Conclusion Our findings suggest that changes of complexion should not be considered when calculating Graybiel's score in hot-humid environment so as to simplify the evaluating process.