Abstract: Maximum metabolic rates (MMR) were determined in plateau pikas and root voles under different photoperiod and temperature acclimation (long day-warm temperature:16L∶8D,23℃;short day-warm temperature:8L∶16D,23℃;long day-cold temperature:16L∶8D,5℃;short day-cold temperature:8L∶16D,5℃).The result in dicated that 1)photoperiod had no effect on MMR of plateau pikas,but cold induced its increase (P<0.01),and temperature was the main physiological cue for seasonal variation in MMR;2)both of short photoperiod and cold could increased MMR in root voles (P<0.01),and they both became the physiological cue for MMR change in root voles.