The current study investigated whether the sex difference on muscle pain following 3㎎/㎏-1 caffeine ingestion was explained by whole body sweat loss volume(WBSLV), muscle pain rating(MPR) and creatine kinase(CK) during pain task (backward walking, gradient -15%, 3㎞ㆍh-1, 85-88 stepsㆍmin-1, 30 min, room temperature 31-32℃ with 40-50% relative humidity). 28 college students volunteered for this investigation and randomized designed and divided into no caffeine (male-6, Con-M: female=7, Con-F) and intake caffeine groups (male-7, Caff-M: female=8, Caff-F). The WBSLV rate was significantly higher in Caff-F them Con-F (p<.05), but not male groups. The MPR was significantly decreased in Caff-F than Con-F at 5min (p<.01), 10min (p<.0l) and 15min (p<.05). However, CK was significantly higher in Caff-F than Con-F, not male groups. Our finding suggest that sex differences in nocicpetive transmission and neuronal sensitization via caffeine, but the lower MPR in female than male in this investigation cause not muscle damage parameters. Therefore, additional research is required to identify the parameters that influence the neurohumoral transmitter of sex difference following caffeine.